Add more robust gettext interpolation handling

While integrating the new delayed messaging gettextutils
functionality into Nova, there were issues with handling
the string interpolation operations. This change adds some
paths for dealing with these cases, such as non-deep-copyable
parameters, and python code-like objects. Also, adds some
much needed test coverage.

Change-Id: I65879875adf7a12fa0d1873167c2efadfc23a54b
Merge "Add more robust gettext interpolation handling"