RPL non-storing: fix a bug causing an infinite loop
RPL non-storing: fix a bug causing an infinite loop

It falls into an infinite loop if it goes to the default label in the switch
statement of rpl_srh_get_next_hop() or rpl_process_srh_header().

MohamedSeliem/contiki,MohamedSeliem/contiki,arurke/contiki,arurke/contiki,arurke/contiki,arurke/contiki,arurke/contiki,MohamedSeliem/contiki,MohamedSeliem/contiki,MohamedSeliem/contiki,arurke/contiki,MohamedSeliem/contiki,MohamedSeliem/contiki,arurke/contiki