(PUP-2659) Synchronize all webrick requests.

Puppet had some scattered thread safety code, which was removed in
4da350b, because Puppet itself is not using threads.  However, Webrick
starts a new thread to handle each incoming request.  This was probably
causing subtle problems during simultaneous requests to a webrick
master, but since 3.6.1 the issue became much more noticeable due to the
fix for PUP-2610 merged in 0dc5ad3 which was fixing a case where rack
masters would lose track of newly established environment loaders using
the master settings.  The change to Puppet::Context used a new
mark/rollback method for overriding context making it very obvious when
concurrent threads would collide attempting to rollback the same marker
and exhaust the context stack.

We are fixing this by synchronizing around incoming webrick requests,
effectively serializing their access to Puppet's innards.  Initial
manual benchmarking did not show a significant decrease in performance,
probably because Ruby uses green threads handled by the vm which cannot
take advantage of multiple processors.
(PUP-2659) Add a concurrency acceptance test

It is difficult to test concurrent requests with Beaker as it does not
allow parrallel requests to be made.  I'm using backgrounded subprocess
in a shell script to get around this, and I'm only making direct catalog
requests via curl, since an agent will halt if it spots another's pidfile in
existence on the same node.  Still, this is one of the major calls that
the agent makes, and it does effectively expose PUP-2659 on a
non-synchronized webrick master.
(PUP-2692) Cache function info with the functions

The Puppet::Parser::Functions code used to hold onto two different sets
of information about the loaded functions: a hash of environment name to
environment module, and a hash of *environment* to a hash of function
name to function information. It was assumed that the
Puppet::Node::Environment class was written to properly work as a hash
key since it implemented both hash() and ==(). This assumption being
true would have meant that different instances for the same environment
would be the same key and the second hash above would not grow beyond a
reasonable size for the number of environments.

It turns out that to be a proper hash key a class must implement hash()
and eql?() (not ==()). Because Puppet::Node::Environment didn't do this
the hash of function information would just continually grow when
directory environments with an environment_timeout != unlimited was in
use. This is because the Puppet::Node::Environment instance would be
periodically thrown out by the Puppet::Environments::Cached loader and
be recreated, but the Puppet::Parser::Functions hash would hold onto the
old instance.

The fix for this here is to consolidate all of the function information
into a single structure. The function modules now have a few methods to
get the function metadata instead of it being stored separately. This is
completely backwards compatible and does not conflict with any existing
uses of the environment modules since the new methods are on the module
itself and will not be part of the mixin.
(PUP-2692) Correctly implement environment equality

This fixes environment equality to make it work as a hash key. It also
adds tests around this functionality.
Merge pull request #2708 from jpartlow/issue/stable/pup-2659-synchronize-webrick-rest

Issue/stable/pup 2659 synchronize webrick rest
Merge branch 'stable'
Merge pull request #2714 from zaphod42/issue/stable/pup-2692-memory-leak-in-master

(PUP-2692) Fix memory leak in directory environments
(maint) Update file mode for future parser

The future parser preserves number literals as actual numbers. This
causes problems for modes on file resources because 640 is the decimal
number 640 and not the octal 640.
(maint) Stop leaking file handles

File.new(f) results in a file handle being used. The test manifest in
this case ended up leaking file handles which caused the master to run
out of file handles while serving a request. This lead to a consistent
failure on the first thread requesting the catalog where the error
reported was:

  Could not autoload puppet/type/notify: no such file to load -- /usr/lib/ruby/site_ruby/1.8/puppet/type/notify.rb

The error was misleading. The underlying problem was not an ENOENT, but
an EMFILE (Too many open files). By switching to File.read(f) the
manifest will no longer leak file handles.
Merge remote-tracking branch 'upstream/stable'

* upstream/stable:
  (maint) Stop leaking file handles
  (maint) Update file mode for future parser
  (PUP-2692) Correctly implement environment equality
  (PUP-2692) Cache function info with the functions
Merge remote-tracking branch 'upstream/master' into puppet-4

* upstream/master:
  (maint) Stop leaking file handles
  (maint) Update file mode for future parser
  (PUP-2692) Correctly implement environment equality
  (PUP-2692) Cache function info with the functions
  (PUP-2659) Add a concurrency acceptance test
  (PUP-2659) Synchronize all webrick requests.