Allow illegal label names from default search predicate

Ancient user watch filters may be configured with strings that
are not valid label names, e.g. "plugins/defaultuser". At the time
these were created the user was expecting to match a project. Now
they blow up the strict checking in LabelType trying to setup an
object for EqualsLabelPredicate to fail to match.

Be more lenient here to allow the label to fail to match.

Change-Id: I52d45456c67924e1981fbbe52a62adfceeebe869
2 files changed