units: make systemd-journald.service Type=notify

It already calls sd_notify(), so it looks like an oversight.

Without it, its ordering to systemd-journal-flush.service is
non-deterministic and the SIGUSR1 from flushing may kill journald before
it has its signal handlers set up.

https://bugs.freedesktop.org/show_bug.cgi?id=85871
https://bugzilla.redhat.com/show_bug.cgi?id=1159641

Conflicts:
	units/systemd-journald.service.in
udev: Fix parsing of udev.event-timeout kernel parameter.
manager: Ensure user's systemd runtime directory exists.

This mirrors code in dbus.c when creating the private socket and
avoids error messages like:

systemd[1353]: bind(/run/user/603/systemd/notify) failed: No such file or directory
systemd[1353]: Failed to fully start up daemon: No such file or directory
systemctl: when invokes as "reboot -f", sync()

We do this in the clean shutdown path in shutdown.c, hence we should do
is for "reboot -f", too.
shared: create files even if the SELinux policy has no context for them

The SELinux policy defines no context for some files. E.g.:
  $ matchpathcon /run/lock/subsys /dev/mqueue
  /run/lock/subsys        <<none>>
  /dev/mqueue     <<none>>

We still need to be able to create them.
In this case selabel_lookup_raw() returns ENOENT. We should then skip
setfscreatecon(), but still return success.
It was broken since c34255bdb2 ("label: unify code to make directories,
symlinks").
core: watchdog bus properties cannot be both writable and constant
sd-bus: create clean error when a property Set() call with incorrect signature is passed in
selinux-access: fix broken ternary operator

it seems to be a typo introduced by ebcf1f97de4f6b1580ae55eb56b1a3939fe6b602
-                _r = selinux_access_check(_b, _m, _u->source_path ?:_u->fragment_path, (permission), &_error); \
+        ({ Unit *_unit = (unit); selinux_generic_access_check(bus,message, _unit->fragment_path ?: _unit->fragment_path, permission,error); })
nspawn: ignore EEXIST when mounting tmpfs

commit 79d80fc1466512d0ca211f4bfcd9de5f2f816a5a introduced a regression that
prevents mounting a tmpfs if the mount point already exits in the container's
root file system. This commit fixes the problem by ignoring EEXIST.