Rename requires files to standard names.

Rename tools/pip-requires to requirements.txt and tools/test-requires
to test-requirements.txt. These are standard files, and tools in the
general world are growing intelligence about them.

Change-Id: I31fa9fb5e6b1e4656424b4a56f58b71903641875
Fixes: bug #1179008
diff --git a/tools/install_venv.py b/tools/install_venv.py
index 5d4b290..1664b35 100644
--- a/tools/install_venv.py
+++ b/tools/install_venv.py
@@ -62,8 +62,8 @@
 def main(argv):
     root = os.path.dirname(os.path.dirname(os.path.realpath(__file__)))
     venv = os.path.join(root, '.venv')
-    pip_requires = os.path.join(root, 'tools', 'pip-requires')
-    test_requires = os.path.join(root, 'tools', 'test-requires')
+    pip_requires = os.path.join(root, 'requirements.txt')
+    test_requires = os.path.join(root, 'test-requirements.txt')
     py_version = "python%s.%s" % (sys.version_info[0], sys.version_info[1])
     project = 'Tempest'
     install = install_venv.InstallVenv(root, venv, pip_requires, test_requires,