libvirt: Provide a port field for GlusterFS network disks

Some versions of libvirt (RHEL6's 0.10.2) require a port
specification with a GlusterFS network disk, or they reject
the disk with an "XML error: missing port for host" error.

Provide port 24007 as part of the disk specification.

Closes-Bug: #1254820

Change-Id: Iedcce32618813ed093b8e9aa8a69d1219b2118a5
Pass Instance object to get_spice_console virt api

Update the virt API to be defined as taking an Instance object.
Luckily, no real changes are needed in the virt drivers to make this
work.  While the API is changing anyway, pass the context in as well
since we have a TODO to add it to virt API methods when convenient.

Change-Id: I2b2f389aee3f2cee3bb1361958da797735c60e18
Make check more pythonic

Use 'if key in ('metadata', 'system_metadata'):'
instead of 'if key == 'metadata' or key == 'system_metadata''

The reason for the change is:
1. The issue has come up more than once in review cycles
2. It is easier to read

Moving forwards it may be useful if there are extra use cases.

Change-Id: Icd4ab4ebd021720b140f9fdb89d201781388c8ff
Merge "Pass Instance object to get_spice_console virt api"
Merge "libvirt: Provide a port field for GlusterFS network disks"
Merge "Make check more pythonic"