Id507109df80391699074773f4787f74507c4b882 introduced the showmapped
command when attempting to disconnect locally attached rbd volumes.
Unfortunately at the time the test changes incorrectly attempted to
assert the commands made by using has_calls instead of the valid
assert_has_calls method.
This change now corrects this, ensures _get_rbd_args is called to
populate all of the required arguments for the showmapped command and
finally corrects the name stored within the fake showmapped output in
the test.
Change-Id: I7e761828b3799cef720e15ca7896e8e8d6f98182
(cherry picked from commit 71331b0e06a713a0883f0c1199923e0943adcf09)
55cfc97581