vc: Fix duplicate operation discriminator

Operation deduplicator should obviously take the
target device into the account when discriminating
new operations.

Bug: 243334827
Tag: #feature
Test: atest --host bluetooth_vc_test --no-bazel-mode
Change-Id: Ia52234b45e286ac5e74f77073f8dfcdc227cb1f9
Merged-In: Ia52234b45e286ac5e74f77073f8dfcdc227cb1f9
(cherry picked from commit 00e402b3)