tests: ignore QUIT from FTP protocol comparisons

- QUIT is not an important FTP command
- curl only sends it "best effort", meaning it might not be sent
- it is a known "flaky" thing in test output because of this

Closes #14404

tests/data/test1050

@@ -47,6 +47,9 @@ perl -e "print 'Test requires default test client host address' if ( '%CLIENT6IP
 
 # Verify data after the test has been "shot"
 <verify>
+<strip>
+QUIT
+</strip>
 # Strip all valid kinds of EPRT that curl can send
 <strippart>
 s/^(EPRT \|2\|::1\|)(.*)/$1/