fab860aed4 fuzz: Stop nodes in process_message* fuzzers (MarcoFalke)
6666c828e0 fuzz: Give CNode ownership to ConnmanTestMsg in process_message fuzz harness (MarcoFalke)
Pull request description:
Background is that I saw an integer overflow in net_processing
```
#30629113 REDUCE cov: 25793 ft: 142917 corp: 3421/2417Kb lim: 4096 exec/s: 89 rss: 614Mb L: 1719/4096 MS: 1 EraseBytes-
net_processing.cpp:977:25: runtime error: signed integer overflow: 2147483624 + 100 cannot be represented in type 'int'
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior net_processing.cpp:977:25 in
net_processing.cpp:985:9: runtime error: signed integer overflow: -2147483572 - 100 cannot be represented in type 'int'
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior net_processing.cpp:985:9 in
```
Telling from the line numbers, it looks like `nMisbehavior` wrapped around.
Fix that by calling `StopNodes` after each exec, which should clear the node state and thus `nMisbehavior`.
ACKs for top commit:
practicalswift:
ACK fab860aed4
Tree-SHA512: 891c081d5843565d891aec028b6c27ef3fa39bc40ae78238e81d8f784b4d4b49cb870998574725a5159dd03aeeb2e0b9bc3d3bb51d57d1231ef42e3394b2d639
