Change root_maxkeys

Most modern distros have the limit for the maximum root keys at 1000000
but some do not.  Because we are creating a new key for each container
we need to bump this up as the older distros are having this limit at
200.

Using 1000000 as the limit because that is that most distros are setting
this to now.  If someone has this value configured over that we do not
change it.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

daemon/keys_unsupported.go

@@ -0,0 +1,8 @@
+// +build !linux
+
+package daemon
+
+// ModifyRootKeyLimit is an noop on unsupported platforms.
+func ModifyRootKeyLimit() error {
+	return nil
+}