Indoor INS: do not perform correction at 500 hz

Indoor mode right now is a CPU beast because it performs the
correction step every cycle.  This changes it to run as frequently
as it would if the GPS were available.
Attiude: indoor uses strict 10 hz updates now

Emulates the behavior of GPS
Merge pull request #637 from peabody124/ins_indoor

Indoor INS: do not perform correction at 500 hz