test: skip nbd tests under semaphore

The tests seem to fail because of a race: dd gets 0 bytes from
the nbd device. Let's skip this particular test for now.

Author: keszybz

test/semaphore-run

@@ -61,7 +61,7 @@ echo
 echo "============= Running amd64 tests as root =============="
 (
     set -x
-    sudo $(which ninja) -C build test
+    sudo CASYNC_TEST_NBD=0 $(which ninja) -C build test
 )
 
 echo
@@ -99,5 +99,5 @@ echo
 echo "============= Running i386 tests as root =============="
 (
     set -x
-    sudo linux32 $(which ninja) -C build-i386 test
+    sudo CASYNC_TEST_NBD=0 linux32 $(which ninja) -C build-i386 test
 )

test/test-nbd.sh.in

@@ -32,7 +32,7 @@ diff -q $SCRATCH_DIR/test.digest $SCRATCH_DIR/extract2.digest
 if [ $UID = 0 ]; then
     modprobe nbd ||:
 
-    if test -e /dev/nbd0 ; then
+    if [ -e /dev/nbd0 -a ${CASYNC_TEST_NBD:-1} = 1 ]; then
         MKDEV_PID=`@top_builddir@/notify-wait @top_builddir@/casync $PARAMS mkdev $SCRATCH_DIR/test.caibx $SCRATCH_DIR/test-node`
 
         dd if=$SCRATCH_DIR/test-node bs=102400 count=80 | @top_builddir@/test-calc-digest $DIGEST > $SCRATCH_DIR/mkdev.digest