Change suite setup/teardown logic

[federicaagostini]

In the current test suite logic we assume that authn/z with x509 VOMS proxy is enabled in all RSEs. Thus, we use it to setup the environment, i.e. create testsuite directory, upload files, etc..

This assumption is actually not valid for lapp-webdav endopoint.

This issue is for changing the suite setup/teardown logic.
Basically, we can use a condition: if some endpoint does not allow x509 VOMS proxy authz, we set up the environment using tokens.

[federicaagostini]

PR #14