FRR: T4020: Updated CLI options processing for FRR daemons

• Reverted changes from python/vyos/util.py. This may lead to

unnecessary FRR restart during each boot, depending on a default file
content and template, but makes this changeset cleaner.

• Fixed typos in node names (extra > characters).
• Added SNMP module for isisd and ldpd, since they have it compiled

now.