tidy-up: prefer return over exit(), fix fallouts

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

packages/vms/report_openssl_version.c

@@ -48,7 +48,7 @@ int main(int argc, char **argv)
 
   if(argc < 1) {
     puts("report_openssl_version filename");
-    exit(1);
+    return 1;
   }
 
   libptr = dlopen(argv[1], 0);
@@ -65,7 +65,7 @@ int main(int argc, char **argv)
 
   if(!ssl_version) {
     puts("Unable to lookup version of OpenSSL");
-    exit(1);
+    return 1;
   }
 
   version = ssl_version(SSLEAY_VERSION);
@@ -91,9 +91,9 @@ int main(int argc, char **argv)
 
     status = LIB$SET_SYMBOL(&symbol_dsc, &value_dsc, &table_type);
     if(!$VMS_STATUS_SUCCESS(status)) {
-      exit(status);
+      return status;
     }
   }
 
-  exit(0);
+  return 0;
 }