Revert 226762 "Android perf tests: kill adbd on the device after..."

This seems to make matters worse on sharded bots.  Possibly because
killing adbd on one device affects the host's adb connection with other devices.

> Android perf tests: kill adbd on the device after running a test.
> 
> There's some data indicating that adbd on the device sometimes
> spontaneously restores its connection.
> After running a test, let's kill adbd and wait for bit.
> 
> This is a speculative change to try to make the bots healthier.
> 
> BUG=
> 
> Review URL: https://codereview.chromium.org/25574002

TBR=bulach@chromium.org

Review URL: https://codereview.chromium.org/25727009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226980 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 226980