Fixed removing of listening UNIX sockets when "changing binary".

When changing binary, sending a SIGTERM to the new binary's master process
should not remove inherited UNIX sockets unless the old binary's master
process has exited.
diff --git a/src/core/nginx.c b/src/core/nginx.c
index 9fcb0eb..f73e559 100644
--- a/src/core/nginx.c
+++ b/src/core/nginx.c
@@ -492,6 +492,7 @@
             ngx_memzero(ls, sizeof(ngx_listening_t));
 
             ls->fd = (ngx_socket_t) s;
+            ls->inherited = 1;
         }
     }
 
diff --git a/src/core/ngx_connection.c b/src/core/ngx_connection.c
index 3368253..88fefce 100644
--- a/src/core/ngx_connection.c
+++ b/src/core/ngx_connection.c
@@ -1070,7 +1070,8 @@
 
         if (ls[i].sockaddr->sa_family == AF_UNIX
             && ngx_process <= NGX_PROCESS_MASTER
-            && ngx_new_binary == 0)
+            && ngx_new_binary == 0
+            && (!ls[i].inherited || ngx_getppid() != ngx_parent))
         {
             u_char *name = ls[i].addr_text.data + sizeof("unix:") - 1;
 
diff --git a/src/core/ngx_cycle.c b/src/core/ngx_cycle.c
index 95f4bdf..764cf46 100644
--- a/src/core/ngx_cycle.c
+++ b/src/core/ngx_cycle.c
@@ -520,6 +520,7 @@
                     == NGX_OK)
                 {
                     nls[n].fd = ls[i].fd;
+                    nls[n].inherited = ls[i].inherited;
                     nls[n].previous = &ls[i];
                     ls[i].remain = 1;