Sheriffing/Uplift-Sim/Beta-Release

Use Beta update channel like Beta release builds (but not dep builds) do.

build/mozconfig.common.override
  add ac_add_options --enable-update-channel=beta

js/src/moz.build 
 dummy change for SM builds 

try syntax: try: -b do -p all -u all[Ubuntu,10.10,Windows,Android] -t all[Ubuntu,10.10,Windows,Android]