Pull newly merged Olso update for 'is' operator

Pull newly merged Olso update for 'is' operator

A recent update to common/scheduler/filters/extra_specs_ops.py in
Oslo added new 'is' operator to allow Boolean check. The original
commit message was:

"Boolean values for capabilities don't work because extra_specs are
all converted to unicode. The scheduler will then check, for example,
if the boolean 'True' is equal to the unicode string 'True', and will
always return False. This patch allows admins to specify '<is> True'
in extra_specs, which will compare successfully to boolean True."

Notice extra_specs_ops now relies on strutils from Olso, so this
change pull strutils from Oslo as well.

Fix bug: # 1146306

Change-Id: I83adf707c30274a3862aa8034e72c3361fd19952