In order to support more algs with different requirements,
expectation handling is allowed to handle more cases, such as
a wildcard source ip as in the case of SIP.  NAT can also be
skipped in some alg cases.
Expectation_create() was otherwise simplified in the process.

Some renaming was done to support the above changes.

Signed-off-by: Darrell Ball <dlu998@gmail.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>