Fix the explanations of HTTPNotFound for keypair's API

Gets the "explanation" from HTTPNotFound exception and returns
correct message. the commit Ia784e09cda986a421e83c2820dfd0a2267867cdd
has fixed this kind of bug already, but this bug is remained.

Closes-Bug: #1307338
Change-Id: I6811eecba86938e4253f437b7677cb7e4468fd67
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
Deprecate instance_destroy() from conductor

This deprecates the instance_destroy() method from conductor,
which is no longer used.

Related to blueprint compute-manager-objects-juno

Change-Id: Ifa0ef5fa3c1bf834be7e8f6bebe2a8ebcae9147e
Deprecate compute_unrescue() from conductor

This deprecates the compute_unrescue() method from conductor, which
is no longer used.

Related to blueprint compute-manager-objects-juno

Change-Id: I3e0670490bd566869de91347218015eed4d37f3e
Merge "Fix the explanations of HTTPNotFound for keypair's API"
Merge "XenAPI: Use local rsync rather than remote if possible"
Merge "Deprecate instance_destroy() from conductor"
Merge "Deprecate compute_unrescue() from conductor"