shell_commands: check ICMPv6 echo reply sender
shell_commands: check ICMPv6 echo reply sender

Fixes #11519 by checking the source address when an echo reply is
received by the `ping6` command.

mtausig/RIOT,smlng/RIOT,josephnoir/RIOT,mtausig/RIOT,toonst/RIOT,ant9000/RIOT,ant9000/RIOT,basilfx/RIOT,authmillenon/RIOT,x3ro/RIOT,jasonatran/RIOT,OTAkeys/RIOT,RIOT-OS/RIOT,basilfx/RIOT,aeneby/RIOT,yogo1212/RIOT,authmillenon/RIOT,miri64/RIOT,aeneby/RIOT,RIOT-OS/RIOT,yogo1212/RIOT,miri64/RIOT,rfuentess/RIOT,jasonatran/RIOT,josephnoir/RIOT,josephnoir/RIOT,cladmi/RIOT,OlegHahm/RIOT,OlegHahm/RIOT,OlegHahm/RIOT,toonst/RIOT,toonst/RIOT,OTAkeys/RIOT,x3ro/RIOT,yogo1212/RIOT,RIOT-OS/RIOT,aeneby/RIOT,OTAkeys/RIOT,RIOT-OS/RIOT,authmillenon/RIOT,kYc0o/RIOT,kaspar030/RIOT,mtausig/RIOT,smlng/RIOT,basilfx/RIOT,aeneby/RIOT,authmillenon/RIOT,jasonatran/RIOT,x3ro/RIOT,ant9000/RIOT,jasonatran/RIOT,rfuentess/RIOT,toonst/RIOT,josephnoir/RIOT,jasonatran/RIOT,cladmi/RIOT,kYc0o/RIOT,mtausig/RIOT,kaspar030/RIOT,mtausig/RIOT,yogo1212/RIOT,x3ro/RIOT,kYc0o/RIOT,josephnoir/RIOT,kYc0o/RIOT,kaspar030/RIOT,miri64/RIOT,ant9000/RIOT,authmillenon/RIOT,OlegHahm/RIOT,basilfx/RIOT,RIOT-OS/RIOT,rfuentess/RIOT,aeneby/RIOT,cladmi/RIOT,authmillenon/RIOT,miri64/RIOT,kaspar030/RIOT,kYc0o/RIOT,yogo1212/RIOT,yogo1212/RIOT,basilfx/RIOT,ant9000/RIOT,OTAkeys/RIOT,smlng/RIOT,miri64/RIOT,x3ro/RIOT,cladmi/RIOT,rfuentess/RIOT,toonst/RIOT,smlng/RIOT,kaspar030/RIOT,rfuentess/RIOT,OlegHahm/RIOT,cladmi/RIOT,OTAkeys/RIOT,smlng/RIOT