Exclude filesystem autotests for INTEGRITY

- There is no mounted partition, where we can create/delete files at runtime.
  Tests should be excluded for now.

Pick-to: 6.2 6.3
Change-Id: I1c4db13d35da7d570c4bf787299d829e08951195
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

tests/auto/corelib/io/CMakeLists.txt

@@ -1,4 +1,8 @@
 # Generated from io.pro.
+# There is no mounted filesystem for IO testing on INTEGRITY yet.
+if(INTEGRITY)
+    return()
+endif()
 
 if(QT_FEATURE_private_tests)
     add_subdirectory(qabstractfileengine)