Fixes to make Docker containers properly shutdown
Fixes to make Docker containers properly shutdown

Making a dockerized daemon receive SIGTERM could be very tricky:
firstly, CMD should not use the "shell form", otherwise a "sh -c" process
will possess the PID 1 therefore no one can receive the SIGTERM sent
from "docker stop";
second, the bitsharesentry.sh should call $BITSHARESD with exec, i.e.
let the daemon take the same PID (i.e. 1). Or in another way, a
"trap SIGTERM" trick may be employed to make sure the SIGTERM is
forwarded to the actual daemon process.

bitshares/bitshares-2,bitshares/bitshares-2,bitshares/bitshares-2,bitshares/bitshares-2