Replace fscanf() with fgets() when reading hostapd PID file

This works around some strange hwsim testing issues with UML where the
fscanf() call seemed to hang in signal handler whereas fgets() had no
issues reading the PID string.

Signed-off-by: Jouni Malinen <quic_jouni@quicinc.com>

ap.c

@@ -170,17 +170,19 @@ static enum sigma_cmd_result cmd_ap_ca_version(struct sigma_dut *dut,
 void kill_hostapd_process_pid(struct sigma_dut *dut)
 {
 	FILE *f;
-	int pid, res;
+	int pid;
+	char *res;
 	char path[100];
 	int count;
 
 	f = fopen(SIGMA_DUT_HOSTAPD_PID_FILE, "r");
 	if (!f)
 		return;
-	res = fscanf(f, "%d", &pid);
+	res = fgets(path, sizeof(path), f);
 	fclose(f);
-	if (res != 1)
+	if (!res)
 		return;
+	pid = atoi(res);
 	sigma_dut_print(dut, DUT_MSG_INFO, "Killing hostapd pid %d", pid);
 	kill(pid, SIGTERM);
 	snprintf(path, sizeof(path), "/proc/%d", pid);