### Description I have 2 mtrees defined that get loaded on startup. I have not specified the `db_table` value but have changed each of the values for `tname_column`, `tprefix_column`, and `tvalue_column`.

`kamcmd mtree.summary` and `kamcmd mtree.list` show that the data was successfully loaded. I expected that running `kamcmd mtree.reload` would reload these mtrees from the database. Running this or sending the same command as an http xmlrpc request yields "error: 500 - Mtree Reload Failed". The same error is received if I try to reload a specific mtree. Prior to this version we were successfully reloading these mtrees with MI commands.

### Troubleshooting

#### Reproduction Use the following mtree paramters with a database table that has the name, prefix, and value fields.

``` modparam("mtree", "tname_column", "name") modparam("mtree", "tprefix_column", "prefix") modparam("mtree", "tvalue_column", "value") modparam("mtree", "mtree", "name=some_mtree;dbtable=some_table;type=0;multi=0") ```

Verify the mtrees were successfully created and attempt to reload with the mtree.reload RPC command.

We are not using an mtrees table and this throws an error that the table does not exist (see logs below). Try creating the mtrees table according to the script located at utils/kamctl/mysql/mtree-create.sql and insert the tname, tprefix, and tvalue values used above. The same error is thrown with a different log entry.

#### Log Messages

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Without mtrees table: ``` Apr 4 21:45:51 localhost /usr/local/sbin/kamailio[26416]: ERROR: db_mysql [km_dbase.c:128]: db_mysql_submit_query(): driver error on query: Table 'db_name.mtrees' doesn't exist (1146) Apr 4 21:45:51 localhost /usr/local/sbin/kamailio[26416]: ERROR: <core> [db_query.c:132]: db_do_query_internal(): error while submitting query Apr 4 21:45:51 localhost /usr/local/sbin/kamailio[26416]: ERROR: mtree [mtree_mod.c:724]: mt_load_db_trees(): Error while querying db Apr 4 21:45:51 localhost /usr/local/sbin/kamailio[26416]: ERROR: mtree [mtree_mod.c:928]: rpc_mtree_reload(): cannot re-load mtrees from database ```

With mtrees table: ``` Apr 4 21:41:47 localhost /usr/local/sbin/kamailio[26416]: ERROR: db_mysql [km_dbase.c:128]: db_mysql_submit_query(): driver error on query: Unknown column 'name' in 'field list' (1054) Apr 4 21:41:47 localhost /usr/local/sbin/kamailio[26416]: ERROR: <core> [db_query.c:132]: db_do_query_internal(): error while submitting query Apr 4 21:41:47 localhost /usr/local/sbin/kamailio[26416]: ERROR: mtree [mtree_mod.c:724]: mt_load_db_trees(): Error while querying db Apr 4 21:41:47 localhost /usr/local/sbin/kamailio[26416]: ERROR: mtree [mtree_mod.c:928]: rpc_mtree_reload(): cannot re-load mtrees from database ```

### Additional Information

According to the documentation found here: http://kamailio.org/docs/modules/5.0.x/modules/mtree.html the db_table param should be ignored if a mtree paramter is defined so I would not expect to need the mtrees table. The data is successfully loaded at startup so I believe the issue is just with the reload command. Our kamailio config and database schema has not changed and we were able to reload mtrees successfully with MI commands in previous releases.

* **Kamailio Version** - output of `kamailio -v`

``` version: kamailio 5.0.0 (x86_64/linux) flags: STATS: Off, USE_TCP, USE_TLS, USE_SCTP, TLS_HOOKS, DISABLE_NAGLE, USE_MCAST, DNS_IP_HACK, SHM_MEM, SHM_MMAP, PKG_MALLOC, Q_MALLOC, F_MALLOC, TLSF_MALLOC, DBG_SR_MEMORY, USE_FUTEX, FAST_LOCK-ADAPTIVE_WAIT, USE_DNS_CACHE, USE_DNS_FAILOVER, USE_NAPTR, USE_DST_BLACKLIST, HAVE_RESOLV_RES ADAPTIVE_WAIT_LOOPS=1024, MAX_RECV_BUFFER_SIZE 262144, MAX_LISTEN 16, MAX_URI_SIZE 1024, BUF_SIZE 65535, DEFAULT PKG_SIZE 8MB poll method support: poll, epoll_lt, epoll_et, sigio_rt, select. id: unknown compiled on 14:35:44 Apr 4 2017 with gcc 4.8.5 ```

* **Operating System**:

``` Linux proxy.vagrant.vm 3.10.0-514.6.2.el7.x86_64 #1 SMP Thu Feb 23 03:04:39 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux CentOS Linux release 7.3.1611 (Core) ```