To avoid breaking the control flow and align to majority of code
already using `return`.
`exit()` has the side-effect of suppressing leak detection in cases.
Fix fallouts detected after switching to `return`.
- configure:
- fix `getaddrinfo` run test to call `freeaddrinfo()` to pacify ASAN,
and call `WSACleanup()` to deinit winsock2.
- fix `getifaddrs` run test to call `freeifaddrs()` to pacify ASAN.
- tests/server:
- setup `atexit(win32_cleanup)` via `win32_init()`.
- return 2 instead of 1 on winsock2 init failures.
- sws: goto cleanup instead of `exit()` in `http_connect()`.
Follow-up to 02dfe71937#7235
- tests/client/http:
- cleanup memory to pacify ASAN in `h2-upgrade-extreme`,
`tls-session-reuse`.
- examples:
- block_ip: fix memory leak reported by CI.
- http2-upload: avoid handle leaks.
Untouched `exit()` calls, made from callbacks:
- docs/examples: ephiperfifo.c, ghiper.c, hiperfifo.c
- tests/libtest: lib582.c, lib655.c, lib670.c
- tests/server: tftpd.c
Closes#16507
08c7c937dc