gluster: Fix build break

Fixed build break cause by Change-Id
I6a48482fb8ce06cbe8d30a942538e056c695b195 - the method name should be
executeVdsBrokerCommand() and not ExecuteVdsBrokerCommand().

Change-Id: I46147e917bd9c14b88a6905408597c423d2f21b2
Signed-off-by: Allon Mureinik <amureini@redhat.com>