iperf_api: fix potential descriptor leak

If the pid file remains, but the process has been killed,
the handle will be rewritten without closing.

Signed-off-by: Maks Mishin <[email protected]>

src/iperf_api.c

@@ -4884,6 +4884,7 @@ iperf_create_pidfile(struct iperf_test *test)
 		    }
 		}
 	    }
+        (void)close(fd);
 	}
 
 	/*