Couple more fixes to update manager

 - First, kill syscache before starting pkg updates, since the database
   may be locked read-only

-  Add a new fbsdupdate function, which does freebsd-update in the chroot / prepped BE
   If there are package updates, do these at the same time as freebsd-update

-  Simplify some of the functions, breakout some bits into sub-functions
Merge branch 'master' of github.com:pcbsd/pcbsd