Global "db_connect_retries" parameter

[liviuchircu]

The "retry-on-connect" problem almost looks to be solved on each TCP-oriented database driver. However, retries are often hard-coded (e.g. db_mysql/dbase.c +300), or not even implemented at all (db_mysql/my_con.c +109).

Since this is really a common corner-case scenario for any backend, it would be nice to simply have a global parameter which dictates the number of attempted connect operations, regardless of the backend.

[razvancrainea]

The same thing should be done for db_oracle (e.g. db_oracle/dbase.c + 213) and db_postgres (e.g. db_postgres/dbase.c +173). It should probably also be done for db_unixodbc (db_unixodbc/dbase.c +118).

[eseanucristian]

We've added module parameter max_db_queries for db_postgres module and max_db_queries and max_db_retries module parameters for db_mysql module.