Workaround SSLFile wrong readline prototype and fix bogus tests.

* bzrlib/tests/test_read_bundle.py:
(load_tests): Not all tests are parametrized.
(TestDeprecations): Deprecate read_bundle_from_url.
(TestReadBundleFromURL.test_read_mergeable_from_url): Test
read_mergeable_from_url instead of read_bundle_from_url which has
no possible_transports parameter and is deprecated.
(TestReadBundleFromURL.test_read_mergeable_respects_possible_transports):
Fix the test so that it respects the transport class it's supposed
to use.

* bzrlib/transport/http/_urllib2_wrappers.py:
(_ReportingFileSocket.readline): Workaround bug in httplib for
python-2.4 and 2.5.