[server/test] make test filename uniques
To avoid these pytest error when collecting the whole test suite:
import file mismatch:
imported module 'unittest_utils' has this __file__ attribute:
cubicweb/cubicweb/server/test/unittest_utils.py
which is not the same as the test file we want to collect:
cubicweb/cubicweb/test/unittest_utils.py
Move cubicweb/server/test/unittest_security.py to cubicweb/server/test/unittest_security.py
and cubicweb/test/unittest_utils.py to cubicweb/test/unittest_server_utils.py