Fix to display IP Filter settings correctly

[tingung]

Fixes #1078

Summary

Fix to display IP Filter settings correctly

• Code refactor and minor bugs listed below
• Update state with the value from json response to ensure IP Filter object in UI is updated
• Move specificityOptions and typeOptions initialization to constructor
• Move all the validation of the form upon saving to reduce code complexity
• Replace toggle option of RuleSpecificity to use const String of IP_RANGE and SINGLE_IP to make the code simpler and more readable
• Move code to clear SubnetMask just before update to prevent SubnetMask become blank when user switch in between IP_RANGE and SINGLE_IP option

Confirmation video - https://drive.google.com/open?id=1ntAIguD-GgT5ZuAqsLtEscN76-M_qbXG

Notes: I have tested the changes with 9.4.0 RC1.