Update instructions to include pull of tests image before running tests

Change-Id: I42031644e2d77556aba6cf3e1e53fc440f279d81
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>

README.md

@@ -41,6 +41,8 @@ OS_CLOUD=<OPENSTACK_CLOUD>    # OpenStack Cloud defined in $HOME/.config/opensta
 ### Run the tests
 
 ```bash
+# Make sure you are using the latest testing-daily image
+docker pull opensourcemano/tests:testing-daily
 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 \
@@ -73,6 +75,8 @@ docker run --rm=true --name tests -t --env-file envconfig.rc \
 The following line will mount the folder `robot-systest`, including all libraries and testuites, and will execute the testsuite `sol003_01`:
 
 ```bash
+# Make sure you are using the latest testing-daily image as base
+docker pull opensourcemano/tests:testing-daily
 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 \