iotests: Source common.env

Source common.env in the iotests' check script.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

tests/qemu-iotests/check

@@ -103,6 +103,12 @@ then
     export QEMU_NBD_PROG="$build_root/qemu-nbd"
 fi
 
+# we need common.env
+if ! . "$build_iotests/common.env"
+then
+    _init_error "failed to source common.env (make sure the qemu-iotests are run from tests/qemu-iotests in the build tree)"
+fi
+
 # we need common.config
 if ! . "$source_iotests/common.config"
 then