adb: increase `adb [un]root` timeout.

3 seconds isn't generous enough, because if we're rapidly restarting
(e.g. `adb root; adb unroot`), init will wait 5 seconds to restart us.

Test: `adb root && adb unroot`
Change-Id: I353e8d1ee14f3b08416445ff627dea4a49afd9a4
1 file changed