arm: Fixed state mixup in user-level thread switching.
arm: Fixed state mixup in user-level thread switching.

--HG--
extra : rebase_source : 3442a69538187d20b0ae5deeabf861cac7588462

utsav2601/cmpe295A,kishoredbn/barrelfish,8l/barrelfish,BarrelfishOS/barrelfish,BarrelfishOS/barrelfish,mslovy/barrelfish,8l/barrelfish,linusyang/barrelfish,kishoredbn/barrelfish,mslovy/barrelfish,BarrelfishOS/barrelfish,BarrelfishOS/barrelfish,BarrelfishOS/barrelfish,BarrelfishOS/barrelfish,BarrelfishOS/barrelfish,BarrelfishOS/barrelfish,utsav2601/cmpe295A,linusyang/barrelfish,linusyang/barrelfish,mslovy/barrelfish,linusyang/barrelfish,mslovy/barrelfish,kishoredbn/barrelfish,utsav2601/cmpe295A,utsav2601/cmpe295A,8l/barrelfish,kishoredbn/barrelfish,8l/barrelfish,BarrelfishOS/barrelfish,utsav2601/cmpe295A,8l/barrelfish,kishoredbn/barrelfish,mslovy/barrelfish,linusyang/barrelfish,8l/barrelfish,kishoredbn/barrelfish,mslovy/barrelfish,utsav2601/cmpe295A