High: fencing: cl#5093 Stonith per device timeout option

Stonith devices can have per device timeouts for fencing
operations by using the pcmk_<action>_timeout device parameter.
This option takes priority over the default global stonith-timeout
value per device. For example, if the default stonith-timeout=20
and device A has pcmk_off_timeout=60, A will timeout after 60 seconds
when the 'off' operation is being executed.