VMware: Add cinder support to devstack

The patch set adds cinder support to devstack. VMware cinder support
can be found at:
 - Nova - https://review.openstack.org/#/c/40245/
 - Cinder - https://review.openstack.org/#/c/41600/

Change-Id: I0a05643010ea6cfb6635505accc3dcf411fdd419
Fix option for metadata access in nicira neutron plugin

Bug 1211850

Set metadata_mode option rather than enable_metadata_access_network.

Change-Id: Ia85aba4d0dfb3e7b21937cf15aebc629e3705aed
Faster old oslo.config detection

Just search in the path where python searches for modules.
Let's use python for searching, it knows the exact rules.

Change-Id: I659f734c418ab5e56f4956f418af48dfbe054c8a
Add XenServer to GetDistro's logic

This is primarily to satisfy the expectations of various scripts that os_*
variables are defined, and will result in a distro similar to "xs6.1.0-59235p"

Fixes bug 1211001

Change-Id: I951e1eb3a5e25f4d8773a11b15cf38157b6492fe
Added functions for get a ip on an instance

The cause of some gating failure looks like
because of getting ip address on instance.
However current exercise didn't log the return value.
In this commit, we add get_instance_ip function with
error hanlding support, and apply it on the execise.

Change-Id: I8e17ba68093faafe58a98eb780a032368eea38aa
Merge "Faster old oslo.config detection"
Merge "VMware: Add cinder support to devstack"
Merge "Add XenServer to GetDistro's logic"
Merge "Fix option for metadata access in nicira neutron plugin"
Merge "Added functions for get a ip on an instance"