restapi: Add flag to detect kdump before fencing

Enables kdumpDetection flag to be set when adding/updating power
management configuration of host using REST API.

Change-Id: I3208e62cbca121a741fb83d9fafd37935df9c1ba
Bug-Url: https://bugzilla.redhat.com/1079821
Signed-off-by: Martin Perina <mperina@redhat.com>