Camera: Handle duplicate camera Id due to openLegacy support

When HAL supports openLegacy, same camera id can be added more than
once.

Because we now use vector to store API1 compatible camera ids, make
sure no duplicate strings are added.

Test: Vendor camera app using openLegacy, Camera CTS
Bug: 110815837
Change-Id: I327744e102cc75929ebcdf51661f9f4ec7f3acf9