(PUP-2584) Make 404 warning on agent specific and an error.

This changes the general 404 warning issued by the indirection rest
baseclass into being an error if the option :fail_on_404 is passed
as a "query option".

This is then used when asking for a ca certificate, when asking for the
node, when asking for the initial catalog, and when retrieving a catalog
from the master.

The :fail_on_404 will raise an exception, and it is up to the caller to
determine what this means - when retrieving a catalog, there may be
retries etc. By contrast, the request for a ca certificate will fail
immediately on an agent run.

To try this, contact the master with an unknown environment when using
directory environments for the master configuration.

This more specific behavior is wanted because:
* the rest indirection is used for many different things, one of them
being probing through a list of files to use until one is found.
* the use cases where it really matters that master does not respond
with 404 should error out.
Merge pull request #2669 from jpartlow/issue/master/pup-2584-make-404-warning-specific-and-an-error

(PUP-2584) Make 404 warning on agent specific and an error.