Uses vhci port associated with instances number.

Bug: 79779940
Test: build/boot omr1 locally with explicit other ports, run two
instances on gce at the same time and see them both show up in adb
devices, run one after another is already complete and use --vhci_port
to force it to use the same flag and observe failure

Change-Id: I809ad6b6ebedf8813daf663c6b7b5394c644ca4c
(cherry picked from commit dd0dcfe2)