Convert some RDF tests to DrupalUnitTestBase

With patch

Drupal test run
---------------

Tests to be run:
 - RDFa markup for comments (Drupal\rdf\Tests\CommentAttributesTest)
 - RDF mapping CRUD functions (Drupal\rdf\Tests\CrudTest)
 - RDF namespaces serialization test (Drupal\rdf\Tests\GetNamespacesTest)
 - RDF namespaces (Drupal\rdf\Tests\GetRdfNamespacesTest)
 - RDF mapping definition functionality (Drupal\rdf\Tests\MappingDefinitionTest)
 - RDF mapping hook (Drupal\rdf\Tests\MappingHookTest)
 - RDFa markup (Drupal\rdf\Tests\RdfaMarkupTest)
 - RDF mapping tests (Drupal\rdf\Tests\RdfMappingEventTest)
 - RDF site schema test (Drupal\rdf\Tests\SiteSchemaTest)
 - RDF tracker page mapping (Drupal\rdf\Tests\TrackerAttributesTest)

Test run started:
 Monday, January 21, 2013 - 23:40

Test summary
------------

RDFa markup for comments 118 passes, 0 fails, and 0 exceptions
RDF mapping CRUD functions 9 passes, 0 fails, and 0 exceptions
RDF namespaces serialization test 7 passes, 0 fails, and 0 exceptions
RDF namespaces 4 passes, 0 fails, and 0 exceptions
RDF mapping definition functionality 59 passes, 0 fails, and 0 exceptions
RDF mapping hook 5 passes, 0 fails, and 0 exceptions
RDFa markup 37 passes, 0 fails, and 0 exceptions
RDF mapping tests 2 passes, 0 fails, and 0 exceptions
RDF site schema test 2 passes, 0 fails, and 0 exceptions
RDF tracker page mapping 33 passes, 0 fails, and 0 exceptions

Test run duration: 3 min 54 sec

without patch

Drupal test run
---------------

Tests to be run:
 - RDFa markup for comments (Drupal\rdf\Tests\CommentAttributesTest)
 - RDF mapping CRUD functions (Drupal\rdf\Tests\CrudTest)
 - RDF namespaces serialization test (Drupal\rdf\Tests\GetNamespacesTest)
 - RDF namespaces (Drupal\rdf\Tests\GetRdfNamespacesTest)
 - RDF mapping definition functionality (Drupal\rdf\Tests\MappingDefinitionTest)
 - RDF mapping hook (Drupal\rdf\Tests\MappingHookTest)
 - RDFa markup (Drupal\rdf\Tests\RdfaMarkupTest)
 - RDF mapping tests (Drupal\rdf\Tests\RdfMappingEventTest)
 - RDF site schema test (Drupal\rdf\Tests\SiteSchemaTest)
 - RDF tracker page mapping (Drupal\rdf\Tests\TrackerAttributesTest)

Test run started:
 Monday, January 21, 2013 - 23:45

Test summary
------------

RDFa markup for comments 118 passes, 0 fails, and 0 exceptions
RDF mapping CRUD functions 10 passes, 0 fails, and 0 exceptions
RDF namespaces serialization test 7 passes, 0 fails, and 0 exceptions
RDF namespaces 5 passes, 0 fails, and 0 exceptions
RDF mapping definition functionality 59 passes, 0 fails, and 0 exceptions
RDF mapping hook 6 passes, 0 fails, and 0 exceptions
RDFa markup 37 passes, 0 fails, and 0 exceptions
RDF mapping tests 3 passes, 0 fails, and 0 exceptions
RDF site schema test 3 passes, 0 fails, and 0 exceptions
RDF tracker page mapping 33 passes, 0 fails, and 0 exceptions

Test run duration: 4 min 22 sec