test_engine_service remove redundant DummyThreadGroups

Remove DummyThreadGroup assignments, since they are assigning to an
EngineService attribute which no longer exists (it's a legacy from
an older heat-engine implementation)

Change-Id: I60de53e88eeb56ab36ec7f3a697fd856b1a84925
Remove unnecessary coding line

As per PEP 263, a Python file with non-ASCII characters must have a
line with "coding: <some-encoding>". This file is pure ASCII, so the
line is unnecessary.

Change-Id: I73d07bc0d80ac4dab484bf2a311818a5f6489dc0
Implement context manager for stack lock

This is to give the engine service methods a means to use the stack lock
that guarantees it will be released if there is an exception.

Change-Id: I6d0e1e7c22f4e74eeb069f980bc09a14f3740beb
Partial-Bug: #1321011
Use stack lock context manager in abandon & delete

This will ensure that the stack lock is always released when there is an
exception.

Change-Id: I6d65c57d8b92107eb84c5ed1fbfd5eca30bace01
Partial-Bug: #1321011
Remove support for nova volumes

Note this is only supported if for some reason cinder client
is not imported, which seems rather random.

Change-Id: Id57ba93ef8202ba2a513ee21aff02e4dac9ec21e
Merge "Implement context manager for stack lock"
Merge "Use stack lock context manager in abandon & delete"
Merge "Remove unnecessary coding line"
Merge "Remove support for nova volumes"
Merge "test_engine_service remove redundant DummyThreadGroups"