Revert "core: make setting the shutdown watchdog configuration via dbus work"

This reverts commit df6e44c4af.

systemd --version segfaults.

Starting program: /usr/lib/systemd/systemd --version
Missing separate debuginfos, use: debuginfo-install systemd-216-16.fc21.x86_64
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
systemd 218
+PAM +AUDIT +SELINUX +IMA -APPARMOR +SMACK +SYSVINIT +UTMP +LIBCRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ -LZ4 +SECCOMP +BLKID +ELFUTILS +KMOD +IDN

Program received signal SIGSEGV, Segmentation fault.
0x000055555557c9be in main (argc=2, argv=0x7fffffffe4d8) at src/core/main.c:1832
1832            arg_shutdown_watchdog = m->shutdown_watchdog;
(gdb) bt
(gdb) bt full
        m = 0x0

src/core/main.c

@@ -1829,7 +1829,6 @@ int main(int argc, char *argv[]) {
 finish:
         pager_close();
 
-        arg_shutdown_watchdog = m->shutdown_watchdog;
         m = manager_free(m);
 
         for (j = 0; j < ELEMENTSOF(arg_default_rlimit); j++) {