Add a switch to control writing to /proc/sys

Not all environments allow writing to /proc/sys, allow these to be
controlled via config setting.

Author: Alex Harford

bosh-templates/cloud_controller_api_ctl.erb

@@ -68,7 +68,9 @@ case $1 in
     # Configure the core file location
     mkdir -p /var/vcap/sys/cores
     chown vcap:vcap /var/vcap/sys/cores
-    echo /var/vcap/sys/cores/core-%e-%s-%p-%t > /proc/sys/kernel/core_pattern
+    <% if p("cc.tweak_proc_sys") %>
+      echo /var/vcap/sys/cores/core-%e-%s-%p-%t > /proc/sys/kernel/core_pattern
+    <% end %>
 
     ulimit -c unlimited