Low: VirtualDomain: cache domain emulator after start

If libvirt goes down, we want to continue to be able to
monitor the domain. We can do this by looking at the domain's
emulator process. Typically we can get this emulator from the
domain's configuration file, but it is possible that the
configuration file will not have an emulator specified. In this
case libvirt uses whatever the default emulator is. To reliably
be able to monitor domains after libvirt goes down, we need to cache
the emulator path in a temporary file so we can retrieve it later.
Low: VirtualDomain: set crm timeout default so this agent can work outside of pacemaker

We have to set the undocumented OCF_RESKEY_CRM_meta_timeout variable
to test VirtualDomain outside of pacemaker. This patch sets a default
timeout variable so the agent will at least work without that value
being specified. Otherwise stop will fail.
Low: VirtualDomain: Suppress error output when running without pacemaker or libvirtd

We should be able to successfully monitor a resource without
libvirtd or pacemaker being available. This patch suppresses
a bunch of error messages that make the monitor's 'exit 0' success
look a bit confusing.