iotests: fix loading of common.config from tests/ subdir

common.rc assumes it is being sourced from the same directory and
so also tries to source common.config from the current working
directory. With the ability to now have named tests in the tests/
subdir we need to check two locations for common.config.

Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20210204124834.774401-12-berrange@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

tests/qemu-iotests/common.rc

@@ -109,8 +109,14 @@ peek_file_raw()
     dd if="$1" bs=1 skip="$2" count="$3" status=none
 }
 
-
-if ! . ./common.config
+config=common.config
+test -f $config || config=../common.config
+if ! test -f $config
+then
+    echo "$0: failed to find common.config"
+    exit 1
+fi
+if ! . $config
     then
     echo "$0: failed to source common.config"
     exit 1