Added systemd notify support to EPMD

Signed-off-by: Peter Lemenkov <lemenkov@gmail.com>
Unify autoconf macros usage

Don't use both HAVE_SYSTEMD_DAEMON and HAVE_SYSTEMD_SD_DAEMON - use only
the latter one and remove the former one entirely.

Signed-off-by: Peter Lemenkov <lemenkov@gmail.com>