Fix #315: add environment variables to hook scripts

All hook scripts are called with at least one environment variable set,
FINIT_HOOK_NAME, useful when reusing the same hook script for multiple
hook points.  It is set to the string name, also used by the path, e.g.,
hook/net/up.

For all hook points from hook/sys/shutdown and later, FINIT_SHUTDOWN is
also set, to one of:  halt, poweroff, reboot.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

plugins/resolvconf.c

@@ -45,7 +45,7 @@ static void setup(void *arg)
 
 	touch("/etc/resolvconf/run/enable-updates");
 	chdir("/etc/resolvconf/run/interface");
-	run_parts("/etc/resolvconf/update.d", "-i", 0);
+	run_parts("/etc/resolvconf/update.d", "-i", NULL, 0);
 	chdir("/");
 }