btrfs-progs: tests: update stream version checks in misc/058

The send stream v2 is supported if the file exists and does not contain
"1". The previous fix reversed the condition but this does not work on
kernel with v1 only support.

Signed-off-by: David Sterba <dsterba@suse.com>

tests/misc-tests/053-receive-write-encoded/test.sh

@@ -11,7 +11,8 @@ check_prereq btrfs
 setup_root_helper
 prepare_test_dev
 
-if ! grep -s '1$'  "/sys/fs/btrfs/features/send_stream_version"; then
+if ! [ -f "/sys/fs/btrfs/features/send_stream_version" ] ||
+   grep -s '1$' "/sys/fs/btrfs/features/send_stream_version"; then
 	_not_run "kernel does not support send stream >1"
 	exit
 fi