GRPC is logging a *lot* of garbage at info level.
This configures the GRPC logger such that it is only giving us logs when
at debug level and also adds a log field indicating where the logs are
coming from.
containerd is still currently spewing these same log messages and needs
a separate update.
Without this change `docker build` is extremely noisy in the daemon
logs.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>