sysinst::md_cleanup_install(): sed is too large for ramdisk

Hi,

src/distrib/utils/sysinst/arch/{hp300,mvme68k,x68k}/md.c's 
md_cleanup_install() claims that it can't run enable_rc_conf(), as "sed is 
too large for the ramdisk" (comments).

I've changed sysinst to use the newly installed system's sed(1) instead 
now, see rev. 1.144 of src/distrib/utils/sysinst/util.c.

I wonder if there's some good reason to not run enable_rc_conf() on any of 
these platforms now? I cannot test this though, could you?

  - Hubert