Show progress bar till the applyPayload returns

Displaying a progress bar till the applyPayload from update_engine
returns.

Test: m Settings && adb install -r $ANDROID_PRODUCT_OUT/system_ext/priv-app/Settings/Settings.apk
Bug: 295035851
Bug: 298214075
Change-Id: Ic8cf4df700505e7f10185ee0f08225411c6621e5