tests: Fix Permission denied on Fedora

On Fedora 26, start.sh fails with these error messages.

Failed to connect to wpa_supplicant global interface: /tmp/wpas-wlan0  error: Permission denied
Failed to connect to wpa_supplicant global interface: /tmp/wpas-wlan0  error: Permission denied
...

This is because Fedora 26 uses "wheel" group as administrative group.

Signed-off-by: Masashi Honma <masashi.honma@gmail.com>

tests/hwsim/start.sh

@@ -58,6 +58,8 @@ fi
 
 if groups | tr ' ' "\n" | grep -q ^admin$; then
     GROUP=admin
+elif groups | tr ' ' "\n" | grep -q ^wheel$; then
+    GROUP=wheel
 else
     GROUP=adm
 fi