Revert "Pin nova"

We are now using the current config options in nova.conf
I7eb06d70aba99592152559252fb2bf2058dc39c6.
This reverts commit c1da7bb957a2065c604ac0daf7ac534aa554dac1.

Change-Id: I04ce6aee737b7a57400b95951725701ce381ddb8