Configure Max NTP Server limit

[reshmanbablo]

What I did

Maximum NTP Server limit has been added as 10 with an appropriate error message. Ref : NTP Scalability Requirements

How I did it

In config/main.py, Validation code has been added to check whether the maximum NTP server limit is reached or not . An error message has been added when it exceeds the limit.

How to verify it

Issue config ntp add <ip_address> 10 times. After the max limit , error message Error: Max elements limit 10 reached. will be thrown.

Previous command output (if the output of a command-line utility has changed)

New command output (if the output of a command-line utility has changed)