avocado/utils/iso9660.py: initialize base class on PyCDLib backend

And avoid checking for the existence (and readability) of the ISO file
on other backends, given that now it's possible to create ISO files.
Signed-off-by: NCleber Rosa <crosa@redhat.com>

avocado/utils/iso9660.py

@@ -34,7 +34,6 @@ import sys
 import tempfile
 
 from . import process
-from . import path as utils_path
 
 
 try:
@@ -130,7 +129,6 @@ class BaseIso9660(object):
     """
 
     def __init__(self, path):
-        utils_path.check_readable(path)
         self.path = path
 
     def read(self, path):
@@ -382,7 +380,7 @@ class ISO9660PyCDLib(MixInMntDirMount, BaseIso9660):
     def __init__(self, path):
         if not has_pycdlib():
             raise RuntimeError('This class requires the pycdlib library')
-        self.path = path
+        super(ISO9660PyCDLib, self).__init__(path)
         self._iso = None
         self._iso_opened_for_create = False