Fix WebTests to pass db name through command line

In webtest sometimes we need db records for assertions/ to build parameters, by default test suite connect to the 'civicrm_test_dev', now we can pass database name through command line as
-b[database_name]

eg:
tools$ scripts/phpunit -u [user_name] -p[pass] -h [host] -b[db_name] WebTest_Mailing_MailingTest