e1000: Prevent reset task killing itself.

commit 8ce6909f77ba1b7bcdea65cc2388fd1742b6d669 upstream.

Killing reset task while adapter is resetting causes deadlock.
Only kill reset task if adapter is not resetting.
Ref bug #43132 on bugzilla.kernel.org

Signed-off-by: Tushar Dave <tushar.n.dave@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>