[TIMOB-12596] Android: Cookie store should be shared between clients

"On Android in development mode the cookie store appears to be shared across instances of XHR clients, whereas in production mode it does not. clearCookies in Android works on the cookie store of a client instance." A shared cookie store was actually implemented just before the V8 merge, and apparently part of it got clobbered in the merge. See original PR: https://github.com/appcelerator/titanium_mobile/pull/474 In particular, it appears this line went missing: + client.setCookieStore(TiCookieStore.getInstance());