Disable redundant DB initialization on guesagent's start

Reasons:
 - Guestagent uses conductor to communicate with database.
 - No direct connection to DB is required.
   But GA still initializes DB connection on start.
   This prevent running guestagent without MySQL installed in guest,
   which could be useful for datastores other then MySQL.

Changes:
 - This patch disables DB initialization on GA start.

Closes-bug: #1256046
Change-Id: I23dafdfbc7b04c24f1b4ddd714005eb615641cd6

bin/trove-guestagent

@@ -38,7 +38,6 @@ from trove.common.rpc import service as rpc_service
 from oslo.config import cfg as openstack_cfg
 from trove.openstack.common import log as logging
 from trove.openstack.common import service as openstack_service
-from trove.db import get_db_api
 
 CONF = cfg.CONF
 CONF.register_opts([openstack_cfg.StrOpt('guest_id')])
@@ -50,7 +49,6 @@ def main():
     logging.setup(None)
 
     try:
-        get_db_api().configure_db(CONF)
         manager = dbaas.datastore_registry().get(CONF.datastore_manager)
         if not manager:
             msg = ("Manager class not registered for datastore manager %s" %