Update the scion-coord README with MySQL server instructions.
Update the scion-coord README with MySQL server instructions.

ercanucan/scion-coord,mlegner/scion-coord,ercanucan/scion-coord,netsec-ethz/scion-coord,netsec-ethz/scion-coord,chaehni/scion-coord,mlegner/scion-coord,ercanucan/scion-coord,chaehni/scion-coord,mlegner/scion-coord,mlegner/scion-coord,netsec-ethz/scion-coord,ercanucan/scion-coord,netsec-ethz/scion-coord,chaehni/scion-coord,chaehni/scion-coord,ercanucan/scion-coord,netsec-ethz/scion-coord,chaehni/scion-coord,mlegner/scion-coord,chaehni/scion-coord,mlegner/scion-coord,netsec-ethz/scion-coord,ercanucan/scion-coord