Fix call grouping.

We can not assume the only type of call duplication is international
prefix vs. no international prefix. There's also other cases, like in
the US: 1 123-456-7890 vs. (123) 456-7890.

Fixes issue CYAN-345.

Change-Id: I7b40dc6277f8e2dbfc4f6fe3319acc086c3f06fe