Don't s/oslo/base/ for files in the rpc lib.

This breaks some message envelope handling code and is not needed for
any of the source files in rpc/, so just avoid it.

Change-Id: I8519568be5102a5890ae5ed046d6fcebe9bbb198
Revert "Fast serialization of RPC envelopes for Kombu"

This reverts commit 22c497097b0d0bd461be40a7a03290aa0b4179f2.

I'm not convinced that this isn't just a micro-optimization when
compared to the rest of the work that a given OpenStack service performs
as the result of these messages.

The implementation is also problematic.  It depends on using a '\0' byte
as a separator and assumes that '\0' will not exist anywhere else in the
message.  This seems to be asking for trouble.  If future data could
ever have a '\0' in it, this will be broken.  Further, if a user could
get a '\0' in a message directly with user-supplied input, this could
result in a security vulnerability.

Lastly, this has a significant impact on consumers of notifications that
are outside of OpenStack code, which have been the primary use case of
notifications (Ceilometer is changing that to a degree).  I don't think
consumers of notifications should have to implement this deserialization
method.

Change-Id: Ib3163ca98f568bf9f789d4b64bcc6d72e0fcb459
Merge "Don't s/oslo/base/ for files in the rpc lib."