xenapi: Cleanup tar process on glance error

Currently, when the network connection to glance is interrupted, there
is different behaviour on upload and download.

This change ensures the behaviour between the two code paths is more
consistent.

Uploads generally need to be given more time before they timeout, so
to keep a single timeout between upload and download, the timeout is
increased to 90 seconds.

At the same time, it ensures the tar process gets killed when any
issues occur with the communication between the hypervisor and
glance.

Change-Id: Id5396e5d3c1052dc2979476a886412da65e08670
Closes-Bug: #1284596
Merge "xenapi: Cleanup tar process on glance error"
Merge commit 'refs/changes/38/84138/2' of git://gold.eng.hq.xensource.com/git/github/openstack/nova into tmpbranch