tree-wide: Migrate to pidref_safe_fork()

Let's migrate all remaining callers of safe_fork()
to pidref_safe_fork() and get rid of safe_fork().

src/socket-activate/socket-activate.c

@@ -18,6 +18,7 @@
 #include "log.h"
 #include "main-func.h"
 #include "pidfd-util.h"
+#include "pidref.h"
 #include "pretty-print.h"
 #include "process-util.h"
 #include "socket-netlink.h"
@@ -238,7 +239,6 @@ static int exec_process(char * const *argv, int start_fd, size_t n_fds) {
 
 static int fork_and_exec_process(char * const *argv, int fd) {
         _cleanup_free_ char *joined = NULL;
-        pid_t child_pid;
         int r;
 
         assert(!strv_isempty(argv));
@@ -248,9 +248,11 @@ static int fork_and_exec_process(char * const *argv, int fd) {
         if (!joined)
                 return log_oom();
 
-        r = safe_fork("(activate)",
-                      FORK_RESET_SIGNALS | FORK_DEATHSIG_SIGTERM | FORK_RLIMIT_NOFILE_SAFE | FORK_LOG,
-                      &child_pid);
+        _cleanup_(pidref_done) PidRef child_pidref = PIDREF_NULL;
+        r = pidref_safe_fork(
+                        "(activate)",
+                        FORK_RESET_SIGNALS|FORK_DEATHSIG_SIGTERM|FORK_RLIMIT_NOFILE_SAFE|FORK_LOG,
+                        &child_pidref);
         if (r < 0)
                 return r;
         if (r == 0) {
@@ -259,7 +261,7 @@ static int fork_and_exec_process(char * const *argv, int fd) {
                 _exit(EXIT_FAILURE);
         }
 
-        log_info("Spawned '%s' as PID " PID_FMT ".", joined, child_pid);
+        log_info("Spawned '%s' as PID " PID_FMT ".", joined, child_pidref.pid);
         return 0;
 }