Method CONF.set_override to change config option's
value with designated value in unit test, but never check if the
designated vaule is valid. Each config option has a type like StrOpt,
BoolOpt, etc. StrOpt with parameter choices only allows values in set
of choices. In short, each config option has limitation for type
and value. In production code, oslo.conf can ensure user's input is
valid, but in unit test, test methods can pass if we use method
CONF.set_override without parameter enforce_type=True even we pass wrong
type or wrong value to config option. This commit makes sure calling
method CONF.set_override with enforce_type=True and fixes violations.
Note: We can't set enforce_type=True by default in oslo.config now, it
may break all project's unit test. We can switch enforce_type=True by
default when all project fix violations like this commit.
Related-Bug: #1517839
Change-Id: Ia9f6b8a04290f93699fc1f613ce0e841f040d4ae
e0c1653fa8