credential: stop using deprecated property for email

In 44e0b22f (Move to new API, detailed properties take precedence,
2011-09-09) we introduce a new data model for coordinates, in the case
of emails, we have "url_string" fro the "detailed" form and
"coordinate_text", for the "store what user entered" form.

In some places of erp5_credential, we use setDefaultEmailText, which
calls Coordinate.setText which uses the deprecated Coordinate.fromText,
which sets the same value for "url_string" and "coordinate_text", which
seems a questionable behavior, because the data is saved twice and
some code might be using the wrong property.

This changes every usage to the new coordinate_text property
6 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
passed ERP5.CodingStyleTest-Master

01:00:48

passed ERP5.PerformanceTest-Master

00:26:10

failed ERP5.UnitTest-Master

01:21:59

failed ERP5.UnitTest-Master.Medusa

02:04:37

passed SlapOS.Eggs.UnitTest-Master.Python2

00:15:45

passed SlapOS.Eggs.UnitTest-Master.Python3

00:15:13