Expand user in openstack plugin
Expand user in openstack plugin

This patch allows to use relative path such as
--key-file=~/.ssh/id_rsa as well as absolute path
--key-file=/home/user/.ssh/id_rsa

Change-Id: Ic6d8b83d9264b65617c9c5f7ff6b0c646d7cfeb3

redhat-openstack/infrared,redhat-openstack/infrared,redhat-openstack/infrared