rpc_test: Extend error injector with kind
rpc_test: Extend error injector with kind

Now a test can configure one-shot errors (no such tests yet)

Signed-off-by: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@scylladb.com>

scylladb/seastar,syuu1228/seastar,scylladb/seastar,syuu1228/seastar,syuu1228/seastar,scylladb/seastar