libvirt-tests: Add test case for nodesuspend

Test command: virsh nodesuspend <target> <duration>

This command will make host suspend or hibernate, running tests on testing
grid may cause unexpected behavior.

This tests only work when test runner setup a remote host (physical or
virtual) with testing version of libvirt daemon running. After that change
the remote_xxx parameters in configuration file to corresponding value.

Signed-off-by: Hao Liu <hliu@redhat.com>
Fix virsh nodesuspend test case.

* Use more straight forward debugging messages and exception messages.
* Added missed 'raise' keywords. When trying to raise an exception, this will
  make cases false PASS when that hosts is timeout when shutting down.
* Extend upper_tolerance of down time checking from 8 to 15. Apprently some
  hosts will take longer to recover from sleeping.

Signed-off-by: Hao Liu <hliu@redhat.com>
Also check LoginProcessTerminatedError

When creating a remote virsh session to another host, there is a
chance that the remote host is unreachable. In this case we expect
a SKIP rather than an FAIL.

Signed-off-by: Hao Liu <hliu@redhat.com>
nodesuspend: Avoid common remote* parameters

Change common remote* params to nodesuspend_remote* to avoid misuse of
this case by any chances, which might cause catastrophic result.

Signed-off-by: Hao Liu <hliu@redhat.com>
Merge pull request #56 from Hao-Liu/nodesuspend

libvirt-tests: Add test case for nodesuspend