misc/android: use adb exec-out instead of adb shell to avoid buffering
misc/android: use adb exec-out instead of adb shell to avoid buffering

According to

https://stackoverflow.com/questions/46233200/stop-buffering-of-adb-shell-output

the adb exec-out commands avoids the buffering inherent to adb shell.

Let's see if using exec-out will fix the android builder flakyness where
exitcodes or output were sometimes missing.

Updates #30512 (perhaps fixes it).

Change-Id: Ib953ef0262b20730e0d4c332058d29c5066bfeb2
Reviewed-on: https://go-review.googlesource.com/c/164661
Run-TryBot: Elias Naur <1d6e1cf70ec6f9ab28d3ea4b27a49a77654d370e@eliasnaur.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

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