pf :Reduce number of hashing operations when handling source nodes

[vegeta_tuxpowered.net]

Summary

Reduce number of hashing operations when handling source nodes by always having a pointer to the hash row mutex in the source node. Provide macros for handling and asserting the mutex. Calculate the hash only once in pf_find_src_node() and then use this hash in subsequent operations.

Cherry-picked from development of D39880

Sponsored by: InnoGames GmbH

[vegeta_tuxpowered.net]

Removed unnecessary state lock assertion.

[kp]

sys/net/pfvar.h

396

That may want to be mtx_lock((sn)->lock), just for safety.

2160

Should we take the opportunity to turn that int returnlocked into bool returnlocked?

[vegeta_tuxpowered.net]

Updated pointer handing. Changed the flag to boolean.

[kp]

I think this looks good, but I want to give Mateusz some time to take a look too.

[vegeta_tuxpowered.net]

The returnlocked flag is now a booelan.