Fix devstack compatibility
Fix devstack compatibility

Devstack commit 537532931da4103e1a873684476dac6d7fe56489 changed behaviour
of devstack func 'trueorfalse' so, our devstack plugin started behave with
error where this func was used.

Change-Id: I646b66102f60e9a091e09f43882413a9941ec012
Closes-Bug: #1412409

jcsp/manila,redhat-openstack/manila,jcsp/manila,vponomaryov/manila,NetApp/manila,sajuptpm/manila,redhat-openstack/manila,bswartz/manila,NetApp/manila,weiting-chen/manila,openstack/manila,openstack/manila,scality/manila,sajuptpm/manila,weiting-chen/manila,vponomaryov/manila,scality/manila,bswartz/manila