i40e: clear test state bit after all ethtool tests

Fix a bug where the TESTING state was still set when
exiting the ethtool diagnostics.

Change-Id: Ic47950d2e86a67167d1d282256d477cecd86d820
Signed-off-by: Shannon Nelson <shannon.nelson@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Kavindya Deegala <kavindya.s.deegala@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>