Fix incorrect exit status checking in sshutils

Method channel.is_closed() was called for checknig ssh command is
finished, but in some cases command was finished, but channel was
still open. Method exit_status_ready() should be called instead.

Also removed unnecessary call of fileno() and shutdown_write(), and
use select instead of poll.

Closes-Bug: #1263645

Change-Id: I9484fca758370b68553e98e9d4c409b493df1117
Preserve consistency in module namings

We rename several modules in the system (mostly in unit tests) so that their
namings become consistent throughout the code.

"Consistency" means here following certain rules like "name all deploy engine
and server provider modules without _engine.py and _provider.py suffixes" or
"name all unit tests like test_<tested_module>.py".

We also add a couple of new folders in unit tests so that the unit tests
structure strictly resembles that of tested modules.

Blueprint unit-tests-refactoring

Change-Id: Ia7b6afce0d1e20b969b56301e0c9ad0f94cc60e4
Merge "Fix incorrect exit status checking in sshutils"
Prepare instances for SSH access

This patchset is in preparation for a scenario for running a
test/benchmark within an instance.

Change-Id: I94276237fb5b453b194e58ed00df589a3420a6ed
Benchmark scenarios for Rally: run task in instance

This patch allows a user to define a scenario where Nova instances are
created, then a script which outputs arbitrary JSON is run, and then the
instance is destroyed.

This allows tests/benchmarks from the instance perspective, as well as
from OS APIs.

blueprint benchmark-scenarios

Change-Id: I4b1f77f5f8c55fe1da41b6ab0b23eb03303ba95f