Haiku: Adapt tst_qstorageinfo unit test to Haiku

On Haiku the '/' filesystem is a pure namespace to mount
in the actual root partition (/boot), and therefor returns
0 for free/available/total bytes.

Change-Id: I60d4786389e01ee271f6cd1aba6f96b19e6a828f
Reviewed-by: Augustin Cavalier <waddlesplash@gmail.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Ivan Komissarov <ABBAPOH@gmail.com>

tests/auto/corelib/io/qstorageinfo/tst_qstorageinfo.cpp

@@ -105,9 +105,11 @@ void tst_QStorageInfo::root()
     QVERIFY(storage.isRoot());
     QVERIFY(!storage.device().isEmpty());
     QVERIFY(!storage.fileSystemType().isEmpty());
+#ifndef Q_OS_HAIKU
     QVERIFY(storage.bytesTotal() > 0);
     QVERIFY(storage.bytesFree() > 0);
     QVERIFY(storage.bytesAvailable() > 0);
+#endif
 }
 
 void tst_QStorageInfo::currentStorage()