Since Go 1.7, context is a standard package. Since Go 1.9, everything
that is provided by "x/net/context" is a couple of type aliases to
types in "context".
Many vendored packages still use x/net/context, so vendor entry remains
for now.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
In info, we only need the number of images, but `CountImages` was
getting the whole map of images and then grabbing the length from that.
This causes a lot of unnecessary CPU usage and memory allocations, which
increases with O(n) on the number of images.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>