FIX installation to enable to install after unstack
FIX installation to enable to install after unstack

Some commands of installation fail when executing after unstack,
because the resouces are remained after unstack.
This patch avoids this situation by allowing the commands to fail and
checking the existence of directories.

Change-Id: I337de2b931b58f4e4cd3d5570f6752cc3f8c1dbd
Closes-Bug: 1569149

openstack/monasca-api,stackforge/monasca-api,openstack/monasca-api,stackforge/monasca-api,sapcc/monasca-api,openstack/monasca-api,sapcc/monasca-api,stackforge/monasca-api,sapcc/monasca-api,stackforge/monasca-api