Otherwise, an HTTP test closely following this one with a tight time
constraint (e.g. 672) could fail because the test server stays sitting
with the wait command for a while.

This will eventually need to be part of the test runner.

Ref: #10818

This speeds up tests by avoiding unnecessary processing.

Ref: #10818

This is code that is directly responsible for running a single test.
This will eventually run in a separate process as part of the parallel
testing project.

Ref: #10818

The tests for an older Valgrind version should probably just be deleted,
given that they're testing for an 18-year-old version.

..rather than by the runner

testutil.pm now contains a few miscellaneous functions that are used in
several places but have no better place to live.  subvariables moves to
servers.pm since most variables that it substitutes relate to servers,
so this is the most appropriate place. Rename a few functions for better
naming consistency.

Ref: #10818
Closes #10995

This changed when the file was renamed in commit cbf5717

This reduces the startup time when there is a known conflict on the
random port chosen for a server.  This was already done for stunnel, but
now it's done for all servers.

If a server couldn't be started on a port, a new one is randomly chosen
and the server is tried again. Avoid accidentally using a
randomly-chosen 0 port offset by adding 1 to the random number.

Found-by: Daniel Stenberg

Calling stopserver() before retrying stunnel due to an error would stop
the dependent server (such as HTTP) meaning stunnel would have nothing
to talk to when it came up. Don't try to force a stop when it didn't
actually start.  Also, don't mark the server as bad for future use when
it starts up on a retry.

Fixes #10976

The verify time must be set in this case, like all cases. An error
message needs to be displayed as well.

The server ports are chosen randomly for each server, but the random
ranges chosen were inconsistently-sized and overlapping. Now, they are
spread out more so at least the first random port chosen for each server
is guaranteed to not also be chosen by another server. The starting port
numbers are also raised to put them in the Ephemeral Port range—not the
range defined by RFC 6335 but the one used by Linux, which starts lower
and gives us more room to work with.

Reported-by: Daniel Stenberg