androidtest.bash: fix pkg dir

androidtest.bash: fix pkg dir

CL 24930 altered the default InstallSuffix
for mobile platforms.
Update androidtest.bash to reflect this.
This reverts CL 16151.

A subsequent CL will make this more robust,
but it will take more discussion and review.
In the meantime, this fixes the build.

Change-Id: Ia19ca2c9bab7b79c9cf24beeca64ecddaa60289c
Reviewed-on: https://go-review.googlesource.com/27927
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Elias Naur <elias.naur@gmail.com>
Reviewed-by: David Crawshaw <crawshaw@golang.org>