Backport https://review.openstack.org/#/c/67771/

Rewrite RemoteClient.get_boot_time()

This is doing conversion between time formats, while we could really
just stay in seconds. This also fixes the method to work for cirros,
which doesn't know about human readable time formats.

Change-Id: Id123d71adb29d169a26f0dde6af00f292fe61d09
Closes-Bug: #1244823
Backport https://review.openstack.org/#/c/67773/

Avoid using assertGreater

This doesn't exist in python 2.6.

Change-Id: I8d41a568ac4c9fc7330077e6643b40eddc071f91
Implement similar trick as https://review.openstack.org/#/c/63001/

Change-Id: Ib3ea97eddc0373f6f16bdd11715e265193a16626
Another similar trick to https://review.openstack.org/#/c/63001/

Change-Id: Ia53a8b3d62090edcfdb01ac62d4dbc5fcf8498ff
Correctly initialize adminPass if using the default image

Change-Id: I477808c9a3ddb31cf81a31b24628400846b2b871