Previously any exception while rolling back the connection_info and
attachment_id of volume bdms would result in the overall attempt to
rollback a LM failing. This change refactors this specific bdm rollback
logic into two self contained methods that ignore by default errors
where possible to allow the LM rollback attempt to continue.
Change-Id: I6bc73e8c8f98d9955f33f309beb8a7c56981b553
(cherry picked from commit 9524a5a1b5)
(cherry picked from commit 377dc5bda9)
(cherry picked from commit 07a04ee171)
a6188ecd79