b=11692

play nicer with parameters on logs upgraded from 1.4.x
- allows updates for old logs whenever we can (i.e. ok for mdc, not for osc)
- allows updates for everyone if --writeconf is specified at tunefs upgrade
time (requires entire fs to be stopped though)
- allows updates of failover partners if --writeconf is specified
- fixes various other little bugs and error messages
- adds a couple of regression tests for upgrading from 1.4.6