Low: mcp: set environment variable which the cluster-glue module needs

Since a setup of HA_LOGFACILITY (https://github.com/ClusterLabs/pacemaker/commit/663ce49, https://github.com/ClusterLabs/pacemaker/commit/4682632) was erased by https://github.com/ClusterLabs/pacemaker/commit/b3b5a57, the log of cluster-glue stonith plugin is not outputted to target specified by PCMK_logfacility.