Apply nova server constraints for resources

Add nova server custom constraint for related
resources.

Change-Id: I0acade2d0b30a9fde1e59cfa7cc5ffb7e0a36850
Implements: blueprint nova-custom-constraints
Apply nova flavor constraint for resources

Add nova flavor custom constraint for related
resources.

Change-Id: I93369bfbf6d0f5f1571283fa1c7f70d5063ccac4
Implements: blueprint nova-custom-constraints
Merge "Apply nova server constraints for resources"
Merge "Apply nova flavor constraint for resources"