Fix optimisation: Correctly extract secondary node
Fix optimisation: Correctly extract secondary node

It is possible for either nodeA or nodeB in a DRBD disk to be the
primary or the secondary. Patch 9825767ad incorrectly assumed nodeB
was the secondary.  Correct this by passing the actual primary to
computeDiskSecondaryNode so it can decide.

Signed-off-by: Brian Foley <a00e555871a6a538e97f8c44307104c884f8e869@google.com>
Reviewed-by: Iustin Pop <acf83a5274f31a43af6b914614365999469c1a31@google.com>

mbakke/ganeti,ganeti/ganeti,andir/ganeti,yiannist/ganeti,mbakke/ganeti,onponomarev/ganeti,yiannist/ganeti,ganeti/ganeti,andir/ganeti,yiannist/ganeti,andir/ganeti,ganeti/ganeti,mbakke/ganeti,onponomarev/ganeti