Add configure flags for gfapi and rbd

Add --disable-{gfapi,rbd} to disable gfapi/rbd support even if available.

Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/configure b/configure
index aa15c5b..5fd0c50 100755
--- a/configure
+++ b/configure
@@ -156,6 +156,10 @@
   ;;
   --disable-numa) disable_numa="yes"
   ;;
+  --disable-rbd) disable_rbd="yes"
+  ;;
+  --disable-gfapi) disable_gfapi="yes"
+  ;;
   --help)
     show_help="yes"
     ;;
@@ -1146,7 +1150,7 @@
   return 0;
 }
 EOF
-if compile_prog "" "-lrbd -lrados" "rbd"; then
+if test "$disable_rbd" != "yes"  && compile_prog "" "-lrbd -lrados" "rbd"; then
   LIBS="-lrbd -lrados $LIBS"
   rbd="yes"
 fi
@@ -1166,7 +1170,7 @@
   return 0;
 }
 EOF
-if compile_prog "" "-lgfapi -lglusterfs" "gfapi"; then
+if test "$disable_gfapi" != "yes"  && compile_prog "" "-lgfapi -lglusterfs" "gfapi"; then
   LIBS="-lgfapi -lglusterfs $LIBS"
   gfapi="yes"
 fi