samba: update systemd service files

Update systemd service files of samba. There are no '@BASE_BINDIR@' and
'@SBINDIR@' in these service files, so drop the original replacement.
Command kill is installed to /bin/kill, then correct in the service files.

Signed-off-by: Kai Kang <kai.kang@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Joe MacDonald <joe_macdonald@mentor.com>