tests: Free test at the end of GetDeviceAliases JSON test

Commit 58b147ad07 added a test for
qemuMonitorGetDeviceAliases but forgot to free the test object at the
end which causes all sort of weird errors and failures when new tests
are added after the GetDeviceAliases.

tests/qemumonitorjsontest.c

@@ -938,6 +938,7 @@ testQemuMonitorJSONGetDeviceAliases(const void *data)
 
 cleanup:
     virStringFreeList(aliases);
+    qemuMonitorTestFree(test);
     return ret;
 }