GN Incremental Install: Reinstall apk regardless of cached values

It sometimes happens that a dev will uninstall an app on device
manually. This currently breaks incremental installs, because the DeviceUtils
cache thinks the apk already exists.

To fix this, verify that cached apk paths actually exist the first time
a cached apk path value is used.

BUG=520082

Review URL: https://codereview.chromium.org/1392813002

Cr-Commit-Position: refs/heads/master@{#352774}
1 file changed