hostapd: fix hostapd vts fail

If wpa_supplicant is running during hostapd vts and there are some
configuration in wpa_supplicant. It will happen both of hostapd and
wpa_supplicant are working with wlan0 interface.

Stop wpa_supplicant before running hostapd vts.

Reproduce step:
1. Connect to Wifi before execute hostapd vts.
2. Run hostapd vts.

Bug: 130207248
Test: vts with below commands
vts-tradefed run commandAndExit vts-hal --skip-all-system-status-check --primary-abi-only --skip-preconditions --module VtsHalWifiHostapdV1_0Target -l INFO
vts-tradefed run commandAndExit vts-hal --skip-all-system-status-check --primary-abi-only --skip-preconditions --module VtsHalWifiHostapdV1_1Target -l INFO

Change-Id: Id91463c2eab3c8c348a91bd978d7ea4aa8d42e85