Import new additions to oslo's processutils.

trycmd() and ssh_execute() have been moved into oslo. Copy the
oslo version here. Conversion will occur in a later review.

Change-Id: I69926af33ff824f712ae2b8e4023233afe1dff2f
Remove duplicate gettext.install() calls

When commit 799a925 moved us to console scripts entry points, we moved
the gettext.install() call into nova/cmd/__init__.py but forgot to
remove it from some of the commands.

Since that move, we've switched to using gettextutils.install() which
supports a $NOVA_LOCALEDIR environment variable ... so calling install()
from these commands will actually break that support.

Change-Id: I1f959704551b35e95c5470a7aef900312db2e223
Merge "Remove duplicate gettext.install() calls"
Merge "Import new additions to oslo's processutils."