proc_sys discovery now ignores I/O errors

In Fedora, one of the /proc/sys values existed, was readable, and
got an I/O error when reading it which caused the script to barf.

Now it just ignores that value and keeps on going.

discovery_agents/proc_sys

@@ -7,7 +7,7 @@
 # This file is part of the Assimilation Project.
 #
 # Author: Alan Robertson <[email protected]>
-# Copyright (C) 2014 - Assimilation Systems Limited
+# Copyright (C) 2014,2015 - Assimilation Systems Limited
 #
 # Free support is available from the Assimilation Project community - http://assimproj.org
 # Paid support is available from Assimilation Systems Limited - http://assimilationsystems.com
@@ -186,7 +186,7 @@ format_dir_contents() {
             continue
         fi
         procdot=$(echo ${proc_name} | sed 's%/%.%g')
-        contents="$(cat "${proc_name}" 2>/dev/null)"
+        contents="$(cat "${proc_name}" 2>/dev/null || true)"
         if
             [ -z "${contents}" ]
         then