Useless code path in import_from_xml causing errors removed

@dianakhuang @sarina @nasthagiri 

It appears as if a useless code path was causing @carsongee errors while importing course from command line.

@carsongee Can you verify that this fixes your issue?
`1) ERROR: test_duplicate_with_url (contentstore.management.commands.tests.test_import.TestImport)

   Traceback (most recent call last):
    cms/djangoapps/contentstore/management/commands/tests/test_import.py line 80 in test_duplicate_with_url
      call_command('import', self.content_dir, self.dupe_dir)
    /edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/django/core/management/__init__.py line 150 in call_command
      return klass.execute(*args, **defaults)
    /edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/django/core/management/base.py line 232 in execute
      output = self.handle(*args, **options)
    cms/djangoapps/contentstore/management/commands/import.py line 51 in handle
      create_new_course_if_not_present=True,
    common/lib/xmodule/xmodule/modulestore/xml_importer.py line 170 in import_from_xml
      store.create_course(dest_course_id.org, dest_course_id.offering)
    common/lib/xmodule/xmodule/modulestore/mongo/base.py line 767 in create_course
      course['_id'] for course in courses
   InvalidLocationError: There are already courses with the given org and course id: [{u'category': u'course', u'name': u'2013_Spring', u'course': u'test_import_course', u'tag': u'i4x', u'org': u'edX', u'revision': None}]

   -------------------- >> begin captured stdout << ---------------------
   Importing.  Data_dir=/tmp/tmpJlk7Ix, course_dirs=(path(u'/tmp/tmpJlk7Ix/tmpBB272d'),)
   Seeding forum roles for course slashes:edX+test_import_course+2013_Spring
   Importing.  Data_dir=/tmp/tmpJlk7Ix, course_dirs=(path(u'/tmp/tmpJlk7Ix/tmpEQsLGu'),)
   
   --------------------- >> end captured stdout << ----------------------
   -------------------- >> begin captured logging << --------------------
   xmodule.modulestore.xml: DEBUG: ========> Starting course import from /tmp/tmpJlk7Ix/tmpBB272d
   xmodule.modulestore.xml: DEBUG: ========> Done with course import from /tmp/tmpJlk7Ix/tmpBB272d
   xmodule.modulestore.xml_importer: DEBUG: Scanning slashes:edX+test_import_course+2013_Spring for course module...
   xmodule.modulestore.xml_importer: DEBUG: ======> IMPORTING course slashes:edX+test_import_course+2013_Spring
   xmodule.modulestore.xml_importer: DEBUG: course data_dir=/tmp/tmpJlk7Ix/tmpBB272d
   root: DEBUG: processing import of module i4x://edX/test_import_course/course/2013_Spring...
   xmodule.modulestore.xml: DEBUG: ========> Starting course import from /tmp/tmpJlk7Ix/tmpEQsLGu
   xmodule.modulestore.xml: DEBUG: ========> Done with course import from /tmp/tmpJlk7Ix/tmpEQsLGu
   --------------------- >> end captured logging << ---------------------`