MFC r300648

MFC r300648

Fix CID 1011370 (Resource leak) in ps.

There is no need to to call strdup() on the value returned by fmt().
The latter calls fmt_argv() which always returns a dynamically
allocated string, and calling strdup() on that leaks the memory
allocated by fmt_argv().  Wave some const magic on ki_args and
ki_env to make the direct assignment happy.  This requires a tweak
to the asprintf() case to avoid a const vs. non-const mismatch.

Reported by:	Coverity
CID:		1011370

git-svn-id: svn://svn.freebsd.org/base/stable/10@301148 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f