New manila images require more then 300Mb of RAM. Otherwise
instance fail to boot with kernel panic.
Based on that we increase flavor for manila and trying to save
RAM in other places. While this works nicely for Ubuntu, CentOS
is still unhappy and needs more work.
But to unblock manila role, CentOS issue will be solved with
follow-up patch only.
Change-Id: I3a3bb59bb6ab8c5cb161e78accbbb45482e595a0