Squish: Starting test cases only if needed files are present

Change-Id: I41a73ce1a4f0d0578cf59af5c69fc19f9ec11dd9
Reviewed-on: http://codereview.qt-project.org/5555
Reviewed-by: Bill King <bill.king@nokia.com>
Reviewed-by: Christian Stenger <christian.stenger@nokia.com>
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>

tests/system/shared/utils.py

@@ -1,5 +1,11 @@
 import tempfile, shutil, os
 
+def neededFilePresent(path):
+    found = os.path.exists(path)
+    if not found:
+        test.fatal("Missing file or directory: " + path)
+    return found
+
 def tempDir():
     Result = os.path.abspath(os.getcwd()+"/../../testing")
     if not os.path.exists(Result):