docs: add special config steps to make CephFS CSI v1.1.0

... work with Ceph v14.2.2 cluster that is not deployed by rook.

Fixes: #486
Signed-off-by: Ramana Raja <rraja@redhat.com>

docs/deploy-cephfs.md

@@ -26,6 +26,20 @@ make image-cephcsi
 
 ## Configuration
 
+**NOTE:** To make CephFS CSI driver version >= 1.1.0 work with Ceph v14.2.2
+cluster (not deployed by rook), you need to add the following settings in the
+`mgr` section of the ceph.conf used by the Ceph manager daemon, and restart the
+Ceph manager daemon.
+
+```
+[mgr]
+client mount uid = 0
+client mount gid = 0
+```
+
+This is due to an [issue](http://tracker.ceph.com/issues/40927) in Ceph v14.2.2
+that should be resolved in v14.2.3.
+
 **Available command line arguments:**
 
 Option              | Default value         | Description