lacp: issue with slave interface admin up after it is added to the bond group [VPP...

lacp: issue with slave interface admin up after it is added to the bond group [VPP-1409]

When the slave interface is admin up after it is added to the bond group,
lacp does not send lacp pdu's to the interface because its periodic timer
is not running.

The issue was the slave interface's variables got reset after the state
machines were initialized.

Change-Id: I2942556ce29a4acc97db3be40293e69bed7b6679
Signed-off-by: Steven <[email protected]>
(cherry picked from commit bf21dc85053931bc597e0fab1112061aa60e986b)