netkit-rwho: Convert to ontarget postinst

Starting the service is something to be done when its booted on target

Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-networking/recipes-netkit/netkit-rwho/netkit-rwho_0.17.bb

@@ -82,8 +82,7 @@ do_install () {
     mkdir -p -m 755 ${D}${localstatedir}/spool/rwho
     chown -R rwhod ${D}${localstatedir}/spool/rwho
 }
-
-pkg_postinst_${PN}-server() {
+pkg_postinst_ontarget_${PN}-server() {
     ${sysconfdir}/init.d/rwhod start
 }