nmtst_main_context_iterate_until() is a macro, and we don't want to restrict the
valid integer type (or range) of the "timeout_msec" argument.
In particular, if the user calculates a timeout with "timestamp_msec -
now_msec", the resulting "timeout_msec" might be a negative gint64.
We should handle that gracefully, and not let it be cast to a huge
unsigned int.
(cherry picked from commit 6cb6888404)
(cherry picked from commit 4d572bea7e)
(cherry picked from commit 95b74a3bde)
(cherry picked from commit 500c63db3c)
e8a5cee1a1