restapi: accept action in remove storage connection

Storage connections delete operation now takes an Action
as optional parameter. The Action object should contain
a Host element from which the connection would be unmounted.

Change-Id: I19a0047ee14962eb8a6d0ab2c4e981913d062612
Bug-Url: https://bugzilla.redhat.com/1117278
Signed-off-by: Daniel Erez <derez@redhat.com>