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
Merge "Disable redundant DB initialization on guesagent's start"