Add ability to save builder data to a disk file

Instances of the RingBuilder class can store its data to a disk file by
the save method and load it by the load method.

blueprint argparse-in-swift-ring-builder

Change-Id: I69fdf0693ca9f520d235a795ecdd2da310dcd5d3
Move common code into a separate function.

test_get_valid and test_get_valid_key2 test tempurl with a
single key and two keys respectively. This change moves common code
for these tests into a separate function.

Change-Id: Ifee211285e27df03d041a4c357b7c1f0c96ed6a8
Add unit tests to ensure TZ variable remains set

See review https://review.openstack.org/29836.

Change-Id: I8ec80202789707f723abfe93ccc9cf1e677e4dc6
Signed-off-by: Peter Portante <peter.portante@redhat.com>
Merge "Add ability to save builder data to a disk file"
Merge "Move common code into a separate function."
Merge "Add unit tests to ensure TZ variable remains set"