qt,tests: Log the actual error code if the assertion fails
* lang/qt/tests/t-addexistingsubkey.cpp ( AddExistingSubkeyJobTest::testAddExistingSubkeyAsync, AddExistingSubkeyJobTest::testAddExistingSubkeySync, AddExistingSubkeyJobTest::testAddExistingSubkeyWithExpiration): Use QCOMPARE instead of QVERIFY for asserting equality.
- GnuPG-bug-id: T6137