Adds collection of VM status metric in OpenStack infra plugin

OpenStack infra collector plugin now collects metrics regarding VM status. It
iterates over vdus and using nova client gets info regarding status. Active
status translates to 1, anything else to 0.

Change-Id: Ia6e36a79a1d20cea07d5c7b3aa2af85b5c0e18d0
Signed-off-by: Benjamin Diaz <bdiaz@whitestack.com>