storage and hash control attributes should also be writable

Afterthought on #2405:

The usage pattern we want to get to is (pseudo vcl, don't take
the syntax for granted)

	sub vcl_whatever_client_sub {
		std.rollback(req);
		set req.<whatever>;
		...
		return (restart);
	}

The hash and storage controls should be no exception

doc/changes.rst

@@ -10,6 +10,10 @@ Varnish Cache Trunk (ongoing)
   Restarts now leave all the request properties in place except for
   ``req.restarts`` and ``req.xid``, which need to change by design.
 
+* ``req.storage``, ``req.hash_ignore_busy`` and
+  ``req.hash_always_miss`` are now accessible from all of the client
+  side subs, not just ``vcl_recv{}``
+
 ================================
 Varnish Cache 5.2.0 (2017-09-15)
 ================================

lib/libvcc/generate.py

@@ -271,7 +271,7 @@ sp_variables = [
 	('req.storage',
 		'STEVEDORE',
 		('client',),
-		('recv',), """
+		('client',), """
 		The storage backend to use to save this request body.
 		"""
 	),
@@ -335,7 +335,7 @@ sp_variables = [
 	('req.hash_ignore_busy',
 		'BOOL',
 		('client',),
-		('recv',), """
+		('client',), """
 		Ignore any busy object during cache lookup. You
 		would want to do this if you have two server looking
 		up content from each other to avoid potential deadlocks.
@@ -344,7 +344,7 @@ sp_variables = [
 	('req.hash_always_miss',
 		'BOOL',
 		('client',),
-		('recv',), """
+		('client',), """
 		Force a cache miss for this request. If set to true
 		Varnish will disregard any existing objects and
 		always (re)fetch from the backend.