MT#9579 add option database.central.dbmaster

For Carrier 3.x only, but it is not harmful for CE/PRO.
It specifies the host for MySQL central->local replication.

Change-Id: I29cdbfa7b47e44f23e79aed1ff9cbae1549ca075
cfg-schema dump: snapshot Wed Oct 15 01:12:54 +0200 2014