Fix description errors in volume fakes

In volumev2 fakes.py. Description of some 'get_*' methods is incorrect.
the error will mislead the user. this patch has already fixed it.

Change-Id: I048e3c2b625c7b54ab19f2b923d4970427f277ff

Author: jiahui.qiang

openstackclient/tests/unit/volume/v2/fakes.py

@@ -480,7 +480,7 @@ def get_backups(backups=None, count=2):
         If backups list is provided, then initialize the Mock object with the
         list. Otherwise create one.
 
-        :param List volumes:
+        :param List backups:
             A list of FakeResource objects faking backups
         :param Integer count:
             The number of backups to be faked
@@ -764,7 +764,7 @@ def get_qoses(qoses=None, count=2):
         If qoses list is provided, then initialize the Mock object with the
         list. Otherwise create one.
 
-        :param List volumes:
+        :param List qoses:
             A list of FakeResource objects faking qoses
         :param Integer count:
             The number of qoses to be faked
@@ -837,7 +837,7 @@ def get_snapshots(snapshots=None, count=2):
         If snapshots list is provided, then initialize the Mock object with the
         list. Otherwise create one.
 
-        :param List volumes:
+        :param List snapshots:
             A list of FakeResource objects faking snapshots
         :param Integer count:
             The number of snapshots to be faked