Clean up more things before running unit tests

Apparently some versions of py3 will drop symlinks in the venv.

Change-Id: I77c52b6ad776ab75c4f9713290cc42a1fcb6e0f7

tox.ini

@@ -13,7 +13,7 @@ deps =
   -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt}
   -r{toxinidir}/requirements.txt
   -r{toxinidir}/test-requirements.txt
-commands = find . -type f -name "*.py[c|o]" -delete
+commands = find . ( -type f -o -type l ) -name "*.py[c|o]" -delete
            find . -type d -name "__pycache__" -delete
            nosetests {posargs:test/unit}
 whitelist_externals = find
@@ -34,6 +34,8 @@ setenv = VIRTUAL_ENV={envdir}
 # But mind that reviews expanding this list may be outstanding in Gerrit.
 [testenv:py35]
 commands =
+  find . ( -type f -o -type l ) -name "*.py[c|o]" -delete
+  find . -type d -name "__pycache__" -delete
   nosetests {posargs:\
       test/unit/account \
       test/unit/cli \