androidtest.bash: wait for device to be ready before using it
androidtest.bash: wait for device to be ready before using it

Updates #23824

Change-Id: I265e3f40192a0a4bf54f608d9408ba0cfef2b69c
Reviewed-on: https://go-review.googlesource.com/c/163457
Run-TryBot: Elias Naur <1d6e1cf70ec6f9ab28d3ea4b27a49a77654d370e@eliasnaur.com>
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

nawawi/go,cloudflare/go,cloudflare/go,CAFxX/go,cloudflare/go,golang/go,CAFxX/go,golang/go,golang/go,cloudflare/go,CAFxX/go,golang/go,akutz/go,cloudflare/go,josharian/go,cloudflare/go,nawawi/go,josharian/go,golang/go,akutz/go,cloudflare/go,nawawi/go,josharian/go,nawawi/go,CAFxX/go,josharian/go,akutz/go,akutz/go,nawawi/go,CAFxX/go,nawawi/go,akutz/go,CAFxX/go,akutz/go,akutz/go,nawawi/go,nawawi/go,josharian/go,golang/go,josharian/go,josharian/go,golang/go,josharian/go,CAFxX/go,akutz/go,CAFxX/go,golang/go,cloudflare/go