gluster: Corrected the event log message

In case of reset for volume options the event log message is corrected
to be diaplyed on the form "Volume Option ${Key}=${Value} reset on
${glusterVolumeName}."

Change-Id: Icd53a3f6a0ef671562a510275d6dd54417669545
Bug-Url: https://bugzilla.redhat.com/956051
Signed-off-by: Shubhendu Tripathi <shtripat@redhat.com>