base: ChooserActivity: Don't show image edit button on multiple targets

Ie52aaab90f678d32d9b67f95d81f86b82d1b9c7c introduced edit button but didn't
took into account that there can be multiple images being shared. This patch
adds a check to ensure that this action is not shown in such cases.

Signed-off-by: Aayush Gupta <aayushgupta219@gmail.com>
Change-Id: I787cd9cfd873242542b330a522bed5df9deb62a4