config: Update zonecfg(1M) link to match config-solaris.md
config: Update zonecfg(1M) link to match config-solaris.md

With the same link update that config-solaris.md got in ea65eb3d
(config-solaris.md: fix info, 2017-04-28, #786), since the old link
404s.

Signed-off-by: W. Trevor King <f75897670c17327c42ab201733fb8a81ff9f4c34@tremily.us>

hqhq/specs,wking/opencontainer-specs,laijs/specs,hqhq/runtime-spec,opencontainers/specs,opencontainers/runtime-spec,wking/opencontainer-runtime-spec