agent instance.
Issue: Some of our complex test requires to reboot compute nodes. In
that scenario, if agent instances are on those computes then those
instances will also be rebooted and running shaker test(s) will be
stopped.
At this time this commit is specifically for shaker's shell class
execution as it writes execution script in /tmp directory and we
know that if system/instance is being rebooted then whatever /tmp
directory contains that will be wiped out. So, if user has a choice
to copy that execution script in some specific directory which is
not being impacted (i.e /mnt, /opt etc) after reboot then through
custom test scripts above condition can be handled
Change-Id: I41f824561e36329d07afc9e798eab44b72aeb01a
159bd35d2f