Log if a quota_usages sync updates usage information

There's some periodic quota_usages syncing that can occur to help
correct any drift that may happen.  It would be useful to log when that
occurs as it may indicate an issue somewhere.

Change-Id: I5b90ab42059ae8ebd0c3890accafb98e70ed037e
Add Docstring to some scheduler/driver.py methods

Add/fix the Docstring of "handle_scheduler_error" and
"instance_update_db" methods

Fix bug 1233546

Change-Id: I133c569fc9496f6d727a72b6d8e4844774cd983d
Remove unused dict functions from utils

These aren't used any more.

Change-Id: Iffb4954691c288c2729171182fd5ee21f8613d2b
Fix libvirt test on systems with real iSCSI devices

The test_libvirt_kvm_iser_volume_with_multipath_getmpdev() test
expects a system with no real iSCSI devices. It actually triggers
an os.walk() of /dev/disk/by-path/ip-*, which will return any
iSCSI devices on the system. Since the test expects none, this
will cause the test to fail.

This patch just stubs that out to return an empty list always.

Change-Id: Ibb3fd18207d013c35487a3eebb336b5f288b703a
Closes-bug: #1234834
Merge "Log if a quota_usages sync updates usage information"
Merge "Fix libvirt test on systems with real iSCSI devices"
Merge "Remove unused dict functions from utils"
Merge "Add Docstring to some scheduler/driver.py methods"