Always enable manila if manila is available

The Manila driver is not WIP, it's used in many
production deployments since the Liberty release.

Set the option ENABLE_CEPH_MANILA to True in case,
so that the manila related setup will occur automatically
if manila is enabled in devstack.

Change-Id: Iec66b201fd775125505fd229963f2d0a5e64c8cb
Signed-off-by: Goutham Pacha Ravi <gouthampravi@gmail.com>

devstack/override-defaults

@@ -3,9 +3,7 @@
 ENABLE_CEPH_CINDER=$(trueorfalse True ENABLE_CEPH_CINDER)
 ENABLE_CEPH_C_BAK=$(trueorfalse True ENABLE_CEPH_C_BAK)
 ENABLE_CEPH_GLANCE=$(trueorfalse True ENABLE_CEPH_GLANCE)
-# Disable Ceph as the default backend for Manila as the
-# CephFS Manila driver is WIP.
-ENABLE_CEPH_MANILA=$(trueorfalse False ENABLE_CEPH_MANILA)
+ENABLE_CEPH_MANILA=$(trueorfalse True ENABLE_CEPH_MANILA)
 ENABLE_CEPH_NOVA=$(trueorfalse True ENABLE_CEPH_NOVA)
 # Do not enable RGW by default as RGW is not tested in upstream CI.
 ENABLE_CEPH_RGW=$(trueorfalse False ENABLE_CEPH_RGW)