Announce pending shutdown on stdout
Announce pending shutdown on stdout

Before:
```
21:35 $ ./cockroach start --insecure
build:     alpha.v1-681-ge48daa5 @ 2016/03/06 02:34:04 (go1.6)
admin:     http://macts.local:26257
sql:       0dd6a2dbff64d6bd9dcca6c009410203e8c727d1@macts.local:26257?sslmode=disable
logs:      cockroach-data/logs
store[0]:  path=cockroach-data
^C
```

After:
```
$ ./cockroach start --insecure
build:     01d3a22ade8d278c732332b63f9e40261c72bba3@ 2016/03/06 02:40:02 (go1.6)
admin:     http://macts.local:26257
sql:       0dd6a2dbff64d6bd9dcca6c009410203e8c727d1@macts.local:26257?sslmode=disable
logs:      cockroach-data/logs
store[0]:  path=cockroach-data
^Cinitiating graceful shutdown of server
server drained and shutdown completed
```

vaibhavarora/cockroach,nieyy/cockroach,cuongdo/cockroach,glycerine/cockroach,paperstreet/cockroach,paperstreet/cockroach,arjun4084346/cockroach,arjun4084346/cockroach,glycerine/cockroach,cockroachdb/cockroach,nieyy/cockroach,maxlang/cockroach,petermattis/cockroach,cuongdo/cockroach,veteranlu/cockroach,veteranlu/cockroach,sunya123/cockroach,vivekmenezes/cockroach,petermattis/cockroach,nieyy/cockroach,vivekmenezes/cockroach,arjun4084346/cockroach,bg451/cockroach,vivekmenezes/cockroach,veteranlu/cockroach,vivekmenezes/cockroach,veteranlu/cockroach,cuongdo/cockroach,petermattis/cockroach,glycerine/cockroach,paperstreet/cockroach,veteranlu/cockroach,paperstreet/cockroach,cockroachdb/cockroach,vaibhavarora/cockroach,vaibhavarora/cockroach,sunya123/cockroach,cuongdo/cockroach,vivekmenezes/cockroach,glycerine/cockroach,arjun4084346/cockroach,cuongdo/cockroach,nieyy/cockroach,sunya123/cockroach,glycerine/cockroach,petermattis/cockroach,cockroachdb/cockroach,maxlang/cockroach,maxlang/cockroach,arjun4084346/cockroach,cockroachdb/cockroach,petermattis/cockroach,vaibhavarora/cockroach,sunya123/cockroach,paperstreet/cockroach,maxlang/cockroach,cockroachdb/cockroach,bg451/cockroach,bg451/cockroach,cuongdo/cockroach,nieyy/cockroach,cockroachdb/cockroach,nieyy/cockroach,vaibhavarora/cockroach,petermattis/cockroach,paperstreet/cockroach,cuongdo/cockroach,veteranlu/cockroach,glycerine/cockroach,sunya123/cockroach,maxlang/cockroach,bg451/cockroach,veteranlu/cockroach,paperstreet/cockroach,sunya123/cockroach,sunya123/cockroach,bg451/cockroach,maxlang/cockroach,arjun4084346/cockroach,glycerine/cockroach,bg451/cockroach,cockroachdb/cockroach,paperstreet/cockroach,sunya123/cockroach,cuongdo/cockroach,maxlang/cockroach,nieyy/cockroach,vaibhavarora/cockroach,vivekmenezes/cockroach,vaibhavarora/cockroach,arjun4084346/cockroach,bg451/cockroach,vaibhavarora/cockroach,cockroachdb/cockroach,glycerine/cockroach,arjun4084346/cockroach,veteranlu/cockroach,maxlang/cockroach,nieyy/cockroach,petermattis/cockroach,vivekmenezes/cockroach,petermattis/cockroach,vivekmenezes/cockroach