Fixes FloatingIPDNS extension 'show' method.

Changes the 'show' method to also work when 'id' is actually
an IP and calls the right method to return a list of DNS entries
for a given domain and IP when the called method is
'v2/{tenant_id}/os-floating-ip-dns/{domain}/entries/{ip}'.

Fixes bug 1089410

Change-Id: I4c424e091209624324754c548e55bbbb304cf79f
Fixes unhandled exception in detach_volume

* Fixes the use case where an exception should have been raised when libvirtd
goes down and a volume is being detached.
* Added unit tests for detach_volume, but skipped one unit test for compute
cells as it is giving an error (TypeError: detach_volume() takes exactly
3 arguments (4 given))

Fixes bug #1101079
Change-Id: I6d83947a0344c5f2d91014de6a2052a881198bb4
Merge "Fixes unhandled exception in detach_volume"
Merge "Fixes FloatingIPDNS extension 'show' method."