scylla-gdb.py: Add "scylla apply" command
scylla-gdb.py: Add "scylla apply" command

Executes given command on all shards.

kjniemi/scylla,raphaelsc/scylla,duarten/scylla,avikivity/scylla,scylladb/scylla,duarten/scylla,kjniemi/scylla,raphaelsc/scylla,scylladb/scylla,scylladb/scylla,kjniemi/scylla,scylladb/scylla,duarten/scylla,avikivity/scylla,raphaelsc/scylla,avikivity/scylla