Fix inconsistency in spec regarding Write consistency guarantees (#261)
Fix inconsistency in spec regarding Write consistency guarantees (#261)

* Fix inconsistency in spec regarding Write consistency guarantees

This updates section 12.1 (Batching and Ordering of Updates) to match
the stronger guarantees in section 13.4 (Parallelism of Read and Write
Requests).

Fixes #258

* Address Stefan's comments

p4lang/p4runtime,p4lang/p4runtime,p4lang/p4runtime