Revert "Add docker exec run a command in privileged mode"

This reverts commit 72a500e9e5929b038816d8bd18d462a19e571c99.

Signed-off-by: Jessica Frazelle <princess@docker.com>

Conflicts:
	daemon/execdriver/native/exec.go
	integration-cli/docker_cli_exec_test.go
	runconfig/exec.go

docs/sources/reference/commandline/cli.md

@@ -1201,7 +1201,6 @@ You'll need two shells for this example.
 
       -d, --detach=false         Detached mode: run command in the background
       -i, --interactive=false    Keep STDIN open even if not attached
-      --privileged=false         Give extended privileges to the command
       -t, --tty=false            Allocate a pseudo-TTY
       -u, --user=                Username or UID (format: <name|uid>[:<group|gid>])