Fix syntax error in lib/tempest

Fix syntax error in lib/tempest:
 Created tempest configuration file:
 21:06:30 ++ CINDER_MULTI_LVM_BACKEND=False
 21:06:30 ++ '[' False == 'True ]'
 21:06:30 /home/stack/devstack/lib/tempest: line 278: [: missing `]'

Change-Id: Ib4e393dad12751bdfb0e6f8fac3accd380a1f760
Merge "Fix syntax error in lib/tempest"