Use printstr for sethostname, setdomainname, and gethostname decoding

The argument passed to sethostname and setdomainname syscalls, as well
as the string returned by gethostname syscall, is not a pathname, so
printpathn is not the right method for its decoding.

* process.c (sys_sethostname, sys_setdomainname): Decode 1st argument
using printstr instead of printpathn.
[ALPHA] (sys_gethostname): Likewise.