ethernet: increase test timeout to account for rs delay / retry

There have been some test failures where an interface did not gain
provisioning or gained provisioning too late due to RS delay (or
potentially a dropped RS?).
Increasing the timeout will hopefully solve those issues.

Test: TH
Bug: 252943771
Bug: 252945396
Bug: 251903916
Change-Id: Icd5edb5da612aab3a5abbc242bac99453ecbde24