Marked tst_qfile as parallel-safe

This test failed a parallel stress test, but seemingly only because it
writes to its own build directory.  This should not interfere with other
running autotests.

Change-Id: I80e548fdb0e915ebe86dcd2205537cb6fee09cff
Reviewed-by: Toby Tomkins <toby.tomkins@nokia.com>
Reviewed-by: Kalle Lehtonen <kalle.ju.lehtonen@nokia.com>

tests/auto/corelib/io/qfile/test/test.pro

@@ -1,4 +1,5 @@
 CONFIG += testcase
+CONFIG += parallel_test
 QT = core-private core network testlib
 TARGET = ../tst_qfile
 SOURCES = ../tst_qfile.cpp