Remove unsafe XML parsing

Move to using xmlutils for all XML parsing. Resolves bug 1190229.
Grizzly backport of Mikal Still's master patch.

Change-Id: I43afb2e188bbea99ea30fe6cb2eb1aeedc4ddfd4
Bump stable/grizzly next version to 2013.1.4

Change-Id: I817767bcb618edf94363aa34dd0eb6ce897ce141
Merge branch 'stable/grizzly' of https://github.com/openstack/nova into grizzly/stable