Update doc example for env to reflect new changes

[brgnepal]

In using the adb with host based tools eclipse and clis
doc section step 5, update the $ vagrant service-manager env doc example to reflect plugin latest changes as

$ vagrant service-manager env docker
# Set the following environment variables to enable access to the
# docker daemon running inside of the vagrant virtual machine:
export DOCKER_HOST=tcp://172.28.128.182:2376
export DOCKER_CERT_PATH=/home/pchandra/test_adb/.vagrant/machines/default/libvirt/docker
export DOCKER_TLS_VERIFY=1
export DOCKER_API_VERSION=1.20

# run following command to configure your shell:
# eval "$(vagrant service-manager env docker)"