systemctl: remove unused variable
build-sys: link libsystemd-login also against libsystemd-daemon-internal

https://bugs.freedesktop.org/show_bug.cgi?id=62085

/usr/lib/gcc/x86_64-pc-linux-gnu/4.6.3/../../../../lib64/libsystemd-login.so:
undefined reference to `sd_listen_fds'

In ee465038ce8 'build-sys: break dependency loop between
libsystemd-id128.la and -shared.la', a partial fix was applied, and
the use of functions from libsystemd-id128 was removed from
libsystemd-shared. Nevertheless, fdset.c was still using sd_listen_fds,
so libsystemd-login should be linked against libysystemd-daemon
or libsystemd-daemon-internal.

Tested-by: Elias Probst <mail@eliasprobst.eu>