journald: fix flushing

Commit 74055aa762 'journalctl: add new --flush command and make use of
it in systemd-journal-flush.service' broke flushing because journald
checks for the /run/systemd/journal/flushed file before opening the
permanent journal. When the creation of this file was postponed,
flushing stoppage ensued.
util: introduce sethostname_idempotent

Function queries system hostname and applies changes only when necessary. Also,
migrate all client of sethostname to sethostname_idempotent while at it.
util: fix copy-paste error and actually set the new hostname

Reported-by: sztanpet on irc
networkd: don't stop the dhcp server when link goes down
man: fix typos in description of SELinuxContextFromNet=
shutdown: do final unmounting only if not running inside the container

If we run in the container then we run in a mount namespace. If namespace dies
then kernel should do unmounting for us, hence we skip unmounting in containers.

Also, it may be the case that we no longer have capability to do umount,
because we are running in the unprivileged container.

See: http://lists.freedesktop.org/archives/systemd-devel/2014-October/023536.html
Revert "sd-bus: check return value of asprintf()"

This reverts commit b1543c4c93855b61b40118e9f14a0423dac2e078.

We check b->address anyway, no need to check the return value,
especially given that the other #ifdef branch don't get the same
treatment.
sd-bus: explicitly cast asprintf() return value away we are not interested in

Let's give coverity a hint what's going on here.
update NEWS
update TODO
calendar: new case 'minutely'
man: document what "minutely" now means
sd-bus: sync kdbus.h (ABI break)

Some comment fixes and header cleanups in kdbus.h, and the task capability
meta information has been factored out to its own struct.
units: tmpfiles-setup-dev - allow unsafe file creation to happen in /dev at boot

This will allow us to mark static device nodes with '!' to indicate that they should only be created at early boot.
man: tmpfiles.d - recommend using b! and c!

We should avoid creating static device nodes at runtime.
shared: in-addr-utils - add default_subnet_mask and default_prefixlen methods

These use the (deprecated) IPv4 address classes to deduce the corresponding subnet masks. This is useful when addresses
without subnet masks and prefix lengths are given.

Make use of these new functions from sd-dhcp-lease.
networkd: network - if no prefixlength is given, try to deduce one from the address class

In case of a class E or F address, ignore the address.
calendarspec: parse 'quarterly' and 'semi-annually' as shortcuts
CODING_STYLE: don't clobber arguments on failure
sd_event_default(): return new event after fork()

thread local storage does not get reinitialised after fork(),
so check pid manually.