test/probe/test_container_failures.py:
An x-backend-put-timestamp header has the internal string format so
the string representation will not necessarily cast to a float; cast
an x-backend-put-timestamp header to a Timestamp first and then cast
to float.
test/probe/test_object_expirer.py:
In a response, an x-backend-timestamp header has the internal string
format whereas an x-timestamp header has the normal format, so the two
will not necessarily be equal. Use x-backend-timestamp consistently to
compare object create_timestamp.
Change-Id: I89ed840e05a5f71388d3bdb596f38f62f901b0bb
Signed-off-by: Alistair Coles <alistairncoles@gmail.com>