defaults: add package to contain server defaults

To reduce the binary size of containerd, we no longer import the
`server` package for only a few defaults. This reduces the size of `ctr`
by 2MB. There are probably other gains elsewhere.

Signed-off-by: Stephen J Day <stephen.day@docker.com>

defaults/defaults.go

@@ -0,0 +1,16 @@
+// Package defaults provides several common defaults for interacting wtih
+// containerd. These can be used on the client-side or server-side.
+package defaults
+
+const (
+	// DefaultRootDir is the default location used by containerd to store
+	// persistent data
+	DefaultRootDir = "/var/lib/containerd"
+	// DefaultStateDir is the default location used by containerd to store
+	// transient data
+	DefaultStateDir = "/run/containerd"
+	// DefaultAddress is the default unix socket address
+	DefaultAddress = "/run/containerd/containerd.sock"
+	// DefaultDebugAddress is the default unix socket address for pprof data
+	DefaultDebugAddress = "/run/containerd/debug.sock"
+)