Update README to include env vars common to test execution

Change-Id: I887eb09ca18b7c5175e6a8a7d3d5892414c38744
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>

README.md

@@ -43,9 +43,11 @@ OS_CLOUD=<OPENSTACK_CLOUD>    # OpenStack Cloud defined in $HOME/.config/opensta
 ```bash
 # Make sure you are using the latest testing-daily image
 docker pull opensourcemano/tests:testing-daily
+export CLOUDS_YAML_FILE="${HOME}/.config/openstack/clouds.yaml"
+export OSM_TESTS_REPO_FOLDER="${HOME}/tests"
 docker run --rm=true --name tests -t --env-file envconfig.rc \
-           -v ~/.config/openstack/clouds.yaml:/etc/openstack/clouds.yaml \
-           -v ~/tests/reports:/robot-systest/reports \
+           -v "${CLOUDS_YAML_FILE}":/etc/openstack/clouds.yaml \
+           -v "${OSM_TESTS_REPO_FOLDER}/reports":/robot-systest/reports \
            opensourcemano/tests:testing-daily \
            -t sanity
 ```
@@ -63,9 +65,11 @@ docker build -f docker/Dockerfile -t osmtests .
 ### Run the tests
 
 ```bash
+export CLOUDS_YAML_FILE="${HOME}/.config/openstack/clouds.yaml"
+export OSM_TESTS_REPO_FOLDER="${HOME}/tests"
 docker run --rm=true --name tests -t --env-file envconfig.rc \
-           -v ~/.config/openstack/clouds.yaml:/etc/openstack/clouds.yaml \
-           -v ~/tests/reports:/robot-systest/reports \
+           -v "${CLOUDS_YAML_FILE}":/etc/openstack/clouds.yaml \
+           -v "${OSM_TESTS_REPO_FOLDER}/reports":/robot-systest/reports \
            osmtests \
            -t sol003_01
 ```
@@ -77,11 +81,14 @@ The following line will mount the folder `robot-systest`, including all librarie
 ```bash
 # Make sure you are using the latest testing-daily image as base
 docker pull opensourcemano/tests:testing-daily
+export CLOUDS_YAML_FILE="${HOME}/.config/openstack/clouds.yaml"
+export OSM_TESTS_REPO_FOLDER="${HOME}/tests"
+export OSM_PACKAGES_FOLDER="${HOME}/osm-packages"
 docker run --rm=true --name tests -t --env-file envconfig.rc \
-           -v ~/.config/openstack/clouds.yaml:/etc/openstack/clouds.yaml \
-           -v ~/tests/robot-systest:/robot-systest \
-           -v ~/tests/reports:/robot-systest/reports \
-           -v ~/osm-packages:/robot-systest/osm-packages \
+           -v "${CLOUDS_YAML_FILE}":/etc/openstack/clouds.yaml \
+           -v "${OSM_TESTS_REPO_FOLDER}/robot-systest":/robot-systest \
+           -v "${OSM_TESTS_REPO_FOLDER}/reports":/robot-systest/reports \
+           -v "${OSM_PACKAGES_FOLDER}":/robot-systest/osm-packages \
            opensourcemano/tests:testing-daily \
            -t sol003_01
 ```