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>
Some test cases might need an ability to execute a command inside a
container (in order to analyse its output and/or exit code). It is a bit
complicated operation to do so using engine API. The function provided
aims to hide this complexity, making exec almost as simple as 'docker
exec'.
NOTE that the exec is synchronous, and command's stdin is closed.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
