runsv: robustify signal handling - SIGTERM to child between vfork and exec could mess things up

While at it, rename bb_signals_recursive_norestart() to bb_signals_norestart():
"recursive" was implying we are setting SA_NODEFER allowing signal handler
to be entered recursively, but we do not do that.

function                                             old     new   delta
bb_signals_norestart                                   -      70     +70
startservice                                         380     394     +14
bb_signals_recursive_norestart                        70       -     -70
------------------------------------------------------------------------------
(add/remove: 1/1 grow/shrink: 1/0 up/down: 84/-70)             Total: 14 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/runit/svlogd.c b/runit/svlogd.c
index 4490492..02c3056 100644
--- a/runit/svlogd.c
+++ b/runit/svlogd.c
@@ -1111,10 +1111,10 @@
 	sigaddset(&blocked_sigset, SIGALRM);
 	sigaddset(&blocked_sigset, SIGHUP);
 	sigprocmask(SIG_BLOCK, &blocked_sigset, NULL);
-	bb_signals_recursive_norestart(1 << SIGTERM, sig_term_handler);
-	bb_signals_recursive_norestart(1 << SIGCHLD, sig_child_handler);
-	bb_signals_recursive_norestart(1 << SIGALRM, sig_alarm_handler);
-	bb_signals_recursive_norestart(1 << SIGHUP, sig_hangup_handler);
+	bb_signals_norestart(1 << SIGTERM, sig_term_handler);
+	bb_signals_norestart(1 << SIGCHLD, sig_child_handler);
+	bb_signals_norestart(1 << SIGALRM, sig_alarm_handler);
+	bb_signals_norestart(1 << SIGHUP, sig_hangup_handler);
 
 	/* Without timestamps, we don't have to print each line
 	 * separately, so we can look for _last_ newline, not first,