Rename vts-core to vts

Bug: 151896491
Test: local build
Exempt-From-Owner-Approval: This CL update suite name vts-core to vts as
the suite name is updated. This CL won't change test logic or behavior.

Merged-In: I562b4dc50765e953800a814a8fd84a01c1b9352b
Change-Id: If871035f66631869d1082a557e2639a2766cd1de
1 file changed