Define HAVE_IBV_LINK_LAYER_ETHERNET if it is supported in libibverbs.

Commit r27211 missed a config file change which broke ompi over
iwarp transports.  

This fixes trac:3726 and should be added to cmr:v1.7.3:reviewer=jsquyres

This commit was SVN r29049.

The following SVN revision numbers were found above:
  r27211 --> open-mpi/ompi@b27862e5c7

The following Trac tickets were found above:
  Ticket 3726 --> https://svn.open-mpi.org/trac/ompi/ticket/3726

config/ompi_check_openfabrics.m4

@@ -198,7 +198,7 @@ AC_DEFUN([OMPI_CHECK_OPENFABRICS],[
                           [#include <infiniband/verbs.h>])
 
            AC_MSG_CHECKING([if RDMAoE support is enabled])
-           AC_DEFINE_UNQUOTED([OMPI_HAVE_RDMAOE], [$$1_have_rdmaoe], [Enable RDMAoE support])
+           AC_DEFINE_UNQUOTED([HAVE_IBV_LINK_LAYER_ETHERNET], [$$1_have_rdmaoe], [Enable RDMAoE support])
            if test "1" = "$$1_have_rdmaoe"; then
                 AC_MSG_RESULT([yes])
            else