Fix --avd flag by removing double quotes

Fixes #730 
This is the same fix made for the adb command in e422d23435cca824d1b423089bd0df232df64fec

This was broken by a change in 0.7.0 where we added quotes around checkSDKBinary present to appease the exec method which expects them.

Spawn does not expect them and fails when double quotes are present