In order to mock constant in unit test, a dependency object is
introduced with minimum code change to achieve this.
Test: atest TetheringTests
Bug: 149467454
Change-Id: I38628daddcb7be7c74846e78d36dc88f065b97d9
Merged-In: I38628daddcb7be7c74846e78d36dc88f065b97d9
(cherry picked from commit 29aee20bfa)