Fix typo in exercise-1 p4tutorial
Fix typo in exercise-1 p4tutorial

Change-Id: Ifc6acc211b46668dc7c20b858eaa090dda9c7f18

gkatsikas/onos,opennetworkinglab/onos,oplinkoms/onos,opennetworkinglab/onos,oplinkoms/onos,oplinkoms/onos,oplinkoms/onos,gkatsikas/onos,oplinkoms/onos,gkatsikas/onos,oplinkoms/onos,opennetworkinglab/onos,oplinkoms/onos,opennetworkinglab/onos,opennetworkinglab/onos,gkatsikas/onos,gkatsikas/onos,gkatsikas/onos,opennetworkinglab/onos