Fixed descriptors leak on process creation.

The leak has been introduced in 325b315e48c4.
This closes #322 issue in GitHub.

src/nxt_process.c

@@ -166,6 +166,14 @@ nxt_process_create(nxt_task_t *task, nxt_process_t *process)
                   init->name, nxt_errno);
 #endif
 
+        if (nxt_slow_path(close(pipefd[0]) != 0)) {
+            nxt_alert(task, "failed to close pipe: %E", nxt_errno);
+        }
+
+        if (nxt_slow_path(close(pipefd[1]) != 0)) {
+            nxt_alert(task, "failed to close pipe: %E", nxt_errno);
+        }
+
         return pid;
     }
 
@@ -230,6 +238,10 @@ nxt_process_create(nxt_task_t *task, nxt_process_t *process)
         goto fail_cleanup;
     }
 
+    if (nxt_slow_path(close(pipefd[1]) != 0)) {
+        nxt_alert(task, "failed to close pipe: %E", nxt_errno);
+    }
+
     process->pid = pid;
 
     nxt_runtime_process_add(task, process);