Remove UNIQUE constraint in Eab common table

In the past, Eab common table was restricted that eab_contact_id must be
unique, but the subid also store in eab common table, which would cause
that eab provider override the capabilities for another subid.

Bug: 193641534
Test: atest
Change-Id: I44c782d20d5d318c584e7a2471367fa23d3a76e2