Move OpenStack update timeout to the settings.py

Make update timeout setting configurable via exporting
environment variable, so it could be tuned for different
deployment scenarios. Also increase timeout value to 1 hour
by default.

Change-Id: I110d9bf1b6c8dd68d38ffc76c0185c55eee87298
Wait until Nailgun's API is ready after VM reset

After resetting Fuel master node we wait until 8000/tcp
port (nginx) is accepting connections. We also should wait
up to 2 minutes until Nailgun's API is ready.

Change-Id: I2360e0dab68ae0a20618f1da64ee5d6b4499e126
Closes-bug: #1368537
Add default REBOOT_TIMEOUT to system tests

Change-Id: I4db420c8e85955dac71dbf5216412ad24b96f405
Related-bug: #1365345
Merge "Wait until Nailgun's API is ready after VM reset"
Merge "Move OpenStack update timeout to the settings.py"
Fix wait until Nailgun's API is ready

Change-Id: Ie3c68297029c21faba3b477973b74d1c15398bb0
Fix 'simple_flat_node_deletion' test

In the simple cluster configuration it is impossible
to remove a single controller now. So let's delete
a compute node instead.

Change-Id: I902200fbbd7096f4039b18a0a59fc2eab692c0cf
Closes-bug: #1368820
Changed value of exit code for test on rollback

Change-Id: Ieb820b25d1d53bbaf7abf9e40251e2c375bb1ba8
Closes-Bug: #1368628