[IMP] on non-rpc debug, only break on non-HTTPException

Completes/improves fd6dde7ca

Because Werkzeug uses/provides flow-control exceptions via
HTTPException (which can be used as straight responses) they are used in
a few places of the web client, when triggering some redirections for
instance.

Breaking into the debugger for such mundane situations is surprising and
inconvenient for developers trying to debug actual issues in the system,
even though HTTPExceptions are by and large not error per-se, and
shouldn't warrant triggering post-mortem debugging.

So in the non-RPC dispatcher, don't post-mortem on HTTPException either.

openerp/http.py

@@ -270,7 +270,8 @@ class WebRequest(object):
            to abitrary responses. Anything returned (except None) will
            be used as response.""" 
         self._failed = exception # prevent tx commit
-        if not isinstance(exception, NO_POSTMORTEM):
+        if not isinstance(exception, NO_POSTMORTEM) \
+                and not isinstance(exception, werkzeug.exceptions.HTTPException):
             openerp.tools.debugger.post_mortem(
                 openerp.tools.config, sys.exc_info())
         raise