Add XML deserializer for qos_manage delete_keys API

XML deserializer is missing for delete_keys API resulting XML format
request not being correctly handled by QoS Manage API extension. This
patch adds XML deserializer for the API.

Also add unittest for qos_manage XML serializer and deserilizer.

Change-Id: I7b3ac6822c52f11b08d767aa55b7107bd0333c36
Closes-bug: #1312553
Remove check_{attach,detach} from volumes API

These methods are not called from anywhere and are likely just a relic
from splitting Cinder out from Nova. Moreover their usage from the API
should really be discouraged as they are inherently racy (the result is
immediately outdated since it is not atomic with anything that might
follow).

Partial-bug: #1302774
Change-Id: I5d79b22b2a1d3c9be429a13d094328fc2075fcd2
Remove unused oslo module and adjust opentstack-common.conf

The issues are detected by new change about update.py
in I68c0108304be8a315bcefe939c22019caab9bc98. This patch
doesn't depend the oslo-incubator patch.
 * remove unused module crypto
 * add missing module loopingcall in openstack-common.conf
 * sort the modules in openstack-common.conf

Change-Id: I9f0fcd3803f89a6902f92d0ea691b9ae0235f64c
Merge "Remove unused oslo module and adjust opentstack-common.conf"
Merge "Remove check_{attach,detach} from volumes API"
Merge "Add XML deserializer for qos_manage delete_keys API"