btl/openib: disable XRC by default

Change the default enable configure option XRC to disabled.  If a user want's
to give it a try they have to explicitly ask for it.

Modify the configury help message to indicate it is not enabled by default.

Related to #3890
Fixes #3969

Signed-off-by: Howard Pritchard <[email protected]>

Author: hppritcha

config/opal_check_openfabrics.m4

@@ -305,8 +305,8 @@ AC_DEFUN([OPAL_CHECK_OPENFABRICS_CM_ARGS],[
     #
     AC_ARG_ENABLE([openib-connectx-xrc],
         [AC_HELP_STRING([--enable-openib-connectx-xrc],
-                        [Enable ConnectX XRC support in the openib BTL. If you do not have InfiniBand ConnectX adapters, you may disable the ConnectX XRC support. If you do not know which InfiniBand adapter is installed on your cluster, leave this option enabled (default: enabled)])],
-                        [enable_connectx_xrc="$enableval"], [enable_connectx_xrc="yes"])
+                        [Enable ConnectX XRC support in the openib BTL. (default: disabled)])],
+                        [enable_connectx_xrc="$enableval"], [enable_connectx_xrc="no"])
     #
     # Unconnect Datagram (UD) based connection manager
     #