tests: fix tst_QSettings on Mac

* Add a check for the case sensitivity of the file system, so that
unit tests can determine whether names of preference files with
different case should generate an error or not.
* Add check for OS X native file format in rainersSyncBugOnMac().

Task-number: QTBUG-32655
Done-with: Liang Qi <liang.qi@digia.com>
Change-Id: I76821653dd4ebc00e20abdbb5b79c1a80290dece
Reviewed-by: Liang Qi <liang.qi@digia.com>
Fix problem with QNetworkAddressEntry returning a invalid netmask.

The ip address should be set before the netmask. The reason for this is
that QNetworkAddressEntry::setNetmask() compares the protocol of the
netmask and the ip, if they don't match the netmask won't be set.

Task-number: QTBUG-33911
Change-Id: Ic344b3653c5dfdc5df912dee16e4dbe069d57d24
Reviewed-by: Peter Hartmann <phartmann@blackberry.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>