make xtrace stateful

instead of forcing xtrace off indescriminatly in functions, capture
the global state before changing xtrace and just restore to the
prior state.

Change-Id: Ifc117c2a8e2d554382ff87fc6885004d74bce187
add indent function

in order to make the output more readable, indent the command
output separate from the echo before the command.

Change-Id: I2783d756f916083f172032b05a2b03d286835f40
suppress devstack console log

instead of printing devstack log to the console, suppress it. We
are already logging it in a sublog. In the normal case, this will
mean our logs are largely the tempest run logs, which are the things
that most people care about (unless something goes wrong).

Change-Id: I438c16d3117e065123afa9ea8c0f7d79a955f9cb
Merge "make xtrace stateful"
Merge "add indent function"
Merge "suppress devstack console log"