lvmlockd: check for multiple lock managers running

lvmlockd: check for multiple lock managers running

When no lock manager for the global lock had been set yet,
and the first global lock request was received, and both
dlm and sanlock were running, lvmlockd would assume it
should use the dlm for the global lock, and would start
the "lvm_global" dlm lockspace automatically.  That's
not always correct, so don't assume the dlm should be used,
fail the lock request, and wait until a VG with a specific
lock type is started to determine the lock manager to use.