fix a regression spotted by chris@. the -f and -I arguments fetch process

fix a regression spotted by chris@.  the -f and -I arguments fetch process
arguments using kvm_getargs, after the pledge() has been made.  someone
brave should refactor this, hoisting the argument fetching to between
kvm_getprocs() and pledge() - storing the argument data as neccessary.
the current situation is also a race -- it fetches the data twice.