Previously, test_object_move_no_such_object_no_tombstone_ancient
would fail intermittently, with an assertion that two timestamps
were almost (but not quite) equal.
This probably comes down to the fact that it's passing floats as
timestamps down into FakeInternalClient's parse(); specifically,
values like 1738046018.2900746 and 1738045066.1442454 are known
to previously fail.
Just fixing the usage doesn't fix the foot-gun, though -- so fix
up parse() to be internally consistent, even if passed a float.
Change-Id: Ide1271dc4ef54b64d2dc99ef658e8340abb0b6ce
3ccf749043