MFC r230873:

MFC r230873:

Try to avoid ambiguity when sysctl returns ENOMEM additionally
checking the returned oldlen: when ENOMEM is due to the supplied
buffer being too short the return oldlen is equal to buffer size.

Without this additional check kvm_getprocs() gets stuck in loop if the
returned ENOMEM was due the exceeded memorylocked limit. This is
easily can be observed running `limits -l 1k top'.

Submitted by:	Andrey Zonov <andrey zonov org>

git-svn-id: svn://svn.freebsd.org/base/stable/8@231551 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f