[connman] Proper D-Bus type for WEP key index in wpa_supplicant D-Bus AP...

[connman] Proper D-Bus type for WEP key index in wpa_supplicant D-Bus API messages

Fixes issues with wpa_supplicant 2.1 and wep.

https://lists.connman.net/pipermail/connman/2013-August/015599.html