Update TEMPEST_README.txt

Change I4bf4a02890a33c4034e4493d1763ed4019fdf46e introduced
using a venv to tempest for running the tests. However,
etc/TEMPEST_README.txt still listed it as a TODO. This
updates the readme with the new behavior.

Change-Id: I730b53996f2785b09f02d014f71e6b97d1e20e75
diff --git a/etc/TEMPEST_README.txt b/etc/TEMPEST_README.txt
index 4f907a0..50fa688 100644
--- a/etc/TEMPEST_README.txt
+++ b/etc/TEMPEST_README.txt
@@ -2,13 +2,6 @@
 -rename the /etc/tempest.conf.sample file to tempest.conf
 -Set the fields in the file to values relevant to your system
 -Set the "authentication" value (basic or keystone_v2 currently supported)
--from the root directory of the project, run "nosetests tempest/tests" to
- run all tests
-
-TODO:
-Use virtualenv to install all needed packages. Till then, the following
-packages must be installed:
--httplib2
--testtools
--paramiko
--nose
\ No newline at end of file
+-From the root directory of the project, run "./run_tests.sh" this will
+create the venv to install the project dependencies and run nosetests tempest
+to run all the tests