We have tstest/integration nowadays.
And this test was one of the lone holdouts using the to-be-nuked
SetControlClientGetterForTesting.
Updates #11649
Change-Id: Icf8a6a2e9b8ae1ac534754afa898c00dc0b7623b
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>