We may not have permission to unlink vp.dir

$ /etc/init.d/varnish_master restart
Stopping Varnish Cache:                                    [FAILED]
Starting Varnish Cache: Assert error in mgt_VccCompile(), mgt/mgt_vcc.c line 302:
  Condition((rmdir(vp.dir)) == 0) not true.
  errno = 13 (Permission denied)

eat all CPU time.

I shouldn't rely on auto-complete too much, especially for only two
characters...

Spotted by @fgsch

It also applies for the 4.1 and 4.0 series.

Refs #1890

Raise a ParseError exception if not.

Fixes #1885.

When varnishtest creates a socket barrier, it will bind a socket and
listen to incoming connections. Once the number of expected connections
is open, connections are closed.

Barrier users only need to connect to the socket, read "nothing" and
block until the connection is closed. It allows virtually any process
to sync with varnishtest. The barrier will provide macros with its
socket information.

This is similar ASSERT_CLI, in order to make socket barriers creation
thread-safe.

This is useful in HTTP loops where it's impossible to predict and use an
array of barriers. All cycles expect the same number of waiters, unlike
semaphores.

They work like semaphores, except that they need explicit initialization
and can optionally be shared between processes.

 Conflicts:
	bin/varnishtest/tests/c00073.vtc

With this you can also filter based on logexpect's vsl arguments.

pattern in the body.

As suggested by Przemek Sobstel on github.

Spotted by: hermunn

In most circumstances the counters vsm_overflow and vsm_overflowed
should be zero. This patch tells the user what he should probably do
when they are not.

(and test the commit email hook)

(But mostly for testing the commit email system.)

Submitted by:	rezan
Fixes:		#1931

Disabled by default.  phk@ ok.

Fixes: #1967