tests: xlate: Use --check to verify replay

tests: xlate: Use --check to verify replay

After applying the translated rule using nft, pass the untranslated rule
to --check instead of dumping the ruleset and performing a string
search. This fixes for mandatory match reordering (e.g. addresses before
interfaces) and minor differences like /32 netmasks or even just
whitespace changes.

Fixes: 223e34b057b95 ("tests: xlate-test: Replay results for reverse direction testing")
Signed-off-by: Phil Sutter <phil@nwl.cc>