vrrp: keepalived: T3847: enable no_tag_node_value_mangle for get_config_dict()

Commit 761631d6 ("vrrp: keepalived: T3847: migrate to get_config_dict()")
switched to the new python function get_config_dict(), when we deal with
tag nodes that can contain a hyphen, we should also set no_tag_node_value_mangle
in order to preserve it.

This caused a dict lookup error as the hyphens in the test scripts got replaced
by an _.