can/isotp: remove timers when closing connection
can/isotp: remove timers when closing connection

Timers were not properly removed leading to hard faults if it fires
after the connection is closed.

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