Correct generation of persistent values

[claucece]

We should test that:

• I delete all otrv4 files on the purple directory,
• I delete persisted values on the prekey server
• I open pidgin with the otr-ng plugin enabled.
• I activate my account and enter my password (if needed)
• I successfully log in
• When I log in, the client profile, prekey profile, private key, forging key, prekey messages, fingerprints, and shared prekey file are correctly generated
• The prekey messages are correctly published (there no error at plugin nor server side), and are persisted on the server

[olabini]

This is now working as expected.