TUN-8427: Fix BackoffHandler's internally shared clock structure

A clock structure was used to help support unit testing timetravel
but it is a globally shared object and is likely unsafe to share
across tests. Reordering of the tests seemed to have intermittent
failures for the TestWaitForBackoffFallback specifically on windows
builds.

Adjusting this to be a shim inside the BackoffHandler struct should
resolve shared object overrides in unit testing.

Additionally, added the reset retries functionality to be inline with
the ResetNow function of the BackoffHandler to align better with
expected functionality of the method.

Removes unused reconnectCredentialManager.

token/token.go

@@ -94,9 +94,10 @@ func errDeleteTokenFailed(lockFilePath string) error {
 // newLock will get a new file lock
 func newLock(path string) *lock {
 	lockPath := path + ".lock"
+	backoff := retry.NewBackoff(uint(7), retry.DefaultBaseTime, false)
 	return &lock{
 		lockFilePath: lockPath,
-		backoff:      &retry.BackoffHandler{MaxRetries: 7},
+		backoff:      &backoff,
 		sigHandler: &signalHandler{
 			signals: []os.Signal{syscall.SIGINT, syscall.SIGTERM},
 		},