Add disabled_reason field to services table

Add a column (String 255) in the services table to store
disabled_reason field.

Change-Id: I3cc03029831bdf6a52e9b65c673794430807aeee
Implements part of bp record-reason-for-disabling-service
make help text more meaningful for cinder docs

Change-Id: I5ccb7801a6df8039c59c7a2f2aacd72907a076a4
Closes-Bug: 1260373
Merge "make help text more meaningful for cinder docs"
Merge "Add disabled_reason field to services table"