avocado.core.tree: Normalize filter entries

There is a great difference between filter path ending with slash or
without it. It might be a source of confusion so this patch normalize
the filter path to match the tree names (without the ending slash).

    --filter-only /path1 /path2/  => /path1,/path2
Signed-off-by: NLukáš Doktor <ldoktor@redhat.com>

avocado/core/tree.py

@@ -533,8 +533,12 @@ def apply_filters(tree, filter_only=None, filter_out=None):
     """
     if filter_only is None:
         filter_only = []
+    else:
+        filter_only = [_.rstrip('/') for _ in filter_only if _]
     if filter_out is None:
         filter_out = []
+    else:
+        filter_out = [_.rstrip('/') for _ in filter_out if _]
     for node in tree.iter_children_preorder():
         keep_node = True
         for path in filter_only: