Limit the data extraction based upon execution time

This commit will add a time waste function if the username is not
present in the database. This is done to prevent the data extraction, in
this case the presence or not, of a username based upon the execution
time for the login process.

In the configuration file, the 'fake_hash' variable is computed with the
input data "fake_data" and the salt "fake_salt" to be transparent about
the data used as input for the hashing function.

The comparison with the 'verify()' function is a boolean (always True in
this case), and is not used in any useful way in the login process.

This waste of time is done even if the risk factor is very small (not to
say inexistent).

The location of this function call is designed to be only present if the
username provided as input does not exists in the database. This is done
to not impact real users.