Set max_template_size to heat's default value

Align default with heat, as this is what most people will be testing.
Patch to make devstack not override the default value:
I77549f2b5e953ff712c50a2b372f6b04725d5eb0

Change-Id: I77c5b59ae9c78489ebd08fd54c865118d3ec00ed
Backport https://review.openstack.org/#/c/61037/

Change-Id: Icf75ca16ea43f7680c492bc780b1e66b94cc1a75
Backport https://review.openstack.org/#/c/63001/

Change-Id: I5c884d2848b7de9e4c26c90eabe8114200c10b21
Backport https://review.openstack.org/#/c/63446/

Use create_server from base.BaseComputeTest

This gets us for free the magic about using the right network.

Change-Id: I4b6cbf8243083cb377323a4aff8de305d5c300f9
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
Yet another similar trick to https://review.openstack.org/#/c/63001/

Change-Id: I50ee7af16e12c52292228393d97d00ff56cf4236
Correctly initialize adminPass if using the default image

Change-Id: I477808c9a3ddb31cf81a31b24628400846b2b871