Create a TetherInterfaceStateMachine when told the interface name.

Test: as follows
    - built
    - flashed
    - booted
    - runtest frameworks-net passes
Bug: 32163131
Bug: 62343300

Merged-In: I542e013aa19fefd3443588c9a81ee59cd669ab6f
Merged-In: I973bdc5b540cce66a9713cebfd5071ad4a4b0a08
Merged-In: I2104ecf8102c8f9541ee2d3ce6589b0081db4fe3
Change-Id: I2104ecf8102c8f9541ee2d3ce6589b0081db4fe3
(cherry picked from commit b912c50b)