[sim] Remove SIM contacts when SIM card gets removed

Thanks! Good point. I didn't know about the function.
But it seems to be very fragile. I couldn't find a string that would match the warning:
```
********* Start testing of TestSimPlugin *********
Config: Using QtTest library 5.2.2, Qt 5.2.2
PASS   : TestSimPlugin::initTestCase()
QWARN  : TestSimPlugin::testClear() [W] CDSimController::performTransientImport:135 - No modem path is configured
INFO   : TestSimPlugin::testClear() Did not receive message: "No modem path is configured"
INFO   : TestSimPlugin::testClear() Did not receive message: "CDSimController::performTransientImport: No modem path is configured"
INFO   : TestSimPlugin::testClear() Did not receive message: "CDSimController::performTransientImport:135 - No modem path is configured"
INFO   : TestSimPlugin::testClear() Did not receive message: "[W] CDSimController::performTransientImport:135 - No modem path is configured"
INFO   : TestSimPlugin::testClear() Did not receive message: "No modem path is configured "
INFO   : TestSimPlugin::testClear() Did not receive message: "CDSimController::performTransientImport: No modem path is configured "
INFO   : TestSimPlugin::testClear() Did not receive message: "CDSimController::performTransientImport:135 - No modem path is configured "
INFO   : TestSimPlugin::testClear() Did not receive message: "[W] CDSimController::performTransientImport:135 - No modem path is configured "
INFO   : TestSimPlugin::testClear() Did not receive message: " No modem path is configured"
INFO   : TestSimPlugin::testClear() Did not receive message: " CDSimController::performTransientImport: No modem path is configured"
INFO   : TestSimPlugin::testClear() Did not receive message: " CDSimController::performTransientImport:135 - No modem path is configured"
INFO   : TestSimPlugin::testClear() Did not receive message: " [W] CDSimController::performTransientImport:135 - No modem path is configured"
FAIL!  : TestSimPlugin::testClear() Not all expected messages were received
PASS   : TestSimPlugin::cleanupTestCase()
Totals: 2 passed, 1 failed, 0 skipped
********* Finished testing of TestSimPlugin *********
```

And the overloaded version accepting QRegularExpression is available in Qt 5.3 only.