Set a non-zero timeout for HTTP client communication with plugin backend.
Set a non-zero timeout for HTTP client communication with plugin
backend.

Currently, the timeout is set to 0, which means no timeout. Set it to a
sane default timeout of 30 seconds.

Signed-off-by: Anusha Ragunathan <ab61560b6c027d679611acf9b4b553fb22d61c05@docker.com>

cpuguy83/cli,thaJeztah/cli,docker/cli,thaJeztah/cli,docker/cli,cpuguy83/cli