Use the list when get information from libvirt

If the libvirt adds new elements to the domain info struct or others,
when use the new libvirt, there will be a valueError (too many values
to unpack). When we get information from libvirt, we should use the
original variable format. This change is for compatibility with upcoming
versions of libvirt which change this signature.

Change-Id: I885a48b730acd618e7cefc93cee3d69226575b7c
Closes-Bug: #1291805
Fix a response header bug in the error middleware

Coerce the Content-Length of the custom error message to a string, not an
integer.  Some pure Python WSGI servers aren't strict and violate the WSGI
specification by automatically converting the value to a string.  Apache,
however, *is* strict, and considers this a 500 Internal Error

Fixes bug 1306963

Change-Id: I9b82ceee096b00c21c3b230dc67701bc40629968
Merge "Fix a response header bug in the error middleware"
Merge "Use the list when get information from libvirt"