policy: fix log message in `IdentitySelectionUpdated`
policy: fix log message in `IdentitySelectionUpdated`

This log message should be at debug, not info level, since it occurs whenever
policy regeneration occurs for an endpoint. Also use `logrus.Fields` for
formatting variables to be in line with convention for Cilium.

Signed-off by: Ian Vernon <ian@cilium.io>

michi-covalent/cilium,cilium/cilium,cilium-team/cilium,cilium/cilium,tgraf/cilium,tgraf/cilium,tklauser/cilium,cilium-team/cilium,tgraf/cilium,tklauser/cilium,cilium/cilium,cilium/cilium,michi-covalent/cilium,tklauser/cilium,michi-covalent/cilium,tgraf/cilium,michi-covalent/cilium,tgraf/cilium,tklauser/cilium,tgraf/cilium,tklauser/cilium,michi-covalent/cilium,cilium/cilium