gluster: Added a plugin under gluster for nrpe configuration.

Added a plugin called nrpe under gluster which is used
for configuring nrpe(a agent used by nagios for monitoring
remote host). This plugin adds the ip address of the
nagios monitoring server to list of allowed machines in
nrpe config file.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1091978
Change-Id: I4faa40e2bf382187907db944f7485c1630fcc0ae
Signed-off-by: ndarshan <dnarayan@redhat.com>