SaveImage: Check and strip userID from URI before accessing

https://github.com/LineageOS/android_frameworks_base/commit/0236d1c5cf434af7f0b1cd71b47316496d1faeca

 started
adding userId in the URIs of screenshots.

Check and only proceed if the user can access the URI. This fixes edit
action as well that is broken due to mentioned change.

Issue: calyxos#1942
Change-Id: I42833a6c61ed5296fbfeda3564400581c2b29b8a
Signed-off-by: Aayush Gupta <aayushgupta219@gmail.com>