[Init] Remove redundant exit(EXIT_FAILURE) instances and replace with return false #11511

While reviewing the bitcoin code I noticed that there are a few exit(EXIT_FAILURE) at various places in the AppInit function.

This function returns to main() which will return/exit with EXIT_FAILURE so returning false instead of an explicit exit(EXIT_FAILURE) seems to be cleaner.

This PR attempts to make things a bit more consistent.

There is a subtle difference between exit() and return from main in that the exit() will not clean up any local vars but I don't think this makes a difference in this case. Using exit() might even lead to bugs in the future where the dtor of local objects are expected to be called.

Please squash.

utACK.

Concept ACK

Concept ACK, this is more consistent, I don't think this was done on purpose, but grew like this because AppInit used to return a exit status directly.

utACK b296bf1496b213eaea53cac0a734679fed7a42f5

utACK b296bf1