title: Migration to sonarqube 4.5.4 failed. Error updating database. Duplicate entry
body: <p>I have upgraded from 4.3.2 to 4.5.4 but during the database migration the attached exception occurs.</p>
  
  <p>could someone help me?</p>
  
  <p>best regards,
  André</p>
  
  <pre><code>2015.07.17 18:59:58 ERROR web[o.s.s.ui.JRubyFacade]  Fail to upgrade database
  
  ### Error updating database.  Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Duplicate entry 'fxcop-CallGCSuppressFinalizeCorrectly' for key 2
  ### The error may involve org.sonar.core.rule.RuleMapper.insert-Inline
  ### The error occurred while setting parameters
  ### SQL: insert into rules       (plugin_rule_key, plugin_name, description, description_format, status, name, plugin_config_key, priority, is_template, language, template_id,     characteristic_id, default_characteristic_id, remediation_function, default_remediation_function,     remediation_coeff, default_remediation_coeff, remediation_offset, default_remediation_offset,     effort_to_fix_description, tags, system_tags, note_data, note_user_login, note_created_at, note_updated_at,     created_at, updated_at)         values (?, ?, ?, ?, ?, ?, ?,       ?, ?, ?, ?,       ?, ?, ?, ?,       ?, ?, ?, ?,       ?, ?, ?, ?, ?, ?,       ?, ?, ?)
  ### Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Duplicate entry 'fxcop-CallGCSuppressFinalizeCorrectly' for key 2
      org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:26)
      ...
  </code></pre>