master: fix TLS enabled updates

As Christian Schroetter reported TLS updates do not work anymore
in 2.0.

This was due to a bug accurately pinpointed by Eero Häkkinen :

   The fetch_service_config method in the file Master/Node.pm is
   changed to use the new _node_read_fast() method which uses
   sysread for reading from a socket and bypasses the TLS layer
   completely.

This commit delegate a _node_read_fast() call to _node_read()
when tls is enabled.

Closes: D:699803
Add changelog entry for 71d0a86
master: remove useless log lines, send to debug

Several log lines were only useful for debugging, but they stayed as INFO.
Removal was necessary as the default is cron gfx again, so /var/log will fill
very fast. It completes 789c59e3a27f5d38cabd02c8f57fec605e6146a8 that only
cared about warnings.

Closes: #1251
graph: remove all extra INFO messages

The start/stop logs are now just plain wrong. Removing them in stable-2.0, as
they are wasting quite a huge diskspace, for almost no value.

And postpone a proper logging scheme for devel.

Closes: #1251
Add changelog entry for 8ad5dda and 4372cdf
release as 2.0.6-4 to sid
Merge branch 'debian' into debian-bpo

Conflicts:
	debian/changelog