XenAPI: Use local rsync rather than remote if possible

Using ssh depends on the host being set up to be able to SSH into
itself which is not a common scenario.  While this is unavoidable for
the current implementation of resize across multiple hosts, if there
is a single host (i.e. a test scenario) or the resize is restricted
to the same host then we can succeed without SSH access

Dependency on Ia310e31d31aaf5c979e41c64af8223202a18e03a is because the
tests will always fail without Ia310 therefore this fix cannot be tested
without taking Ia310 as well.

Closes-bug: 1308064

Change-Id: I15802a1d97d380b1c5b74fc9f92ece2494fe789a
Merge "XenAPI: Use local rsync rather than remote if possible"