test: combined test of dhcp + ntp + dns

[troglobit]

Purpose

Verify statically configured DNS and NTP servers are not lost when receiving servers from a DHCP server.

Depends on:

• Operational status support for DNS and NTP #510

Note: the bare bones setup in this test could be useful even before #510 to quickly set up a device for manual verification.

Stages

1. Set up static IP, DNS, and NTP
   • Verify connectivity
   • Verify DNS resolution
   • Verify NTP sync/server connection
2. Disable static IP, enable DHCP (allow NTP + DNS options)
   • Verify connectivity
   • Verify DNS resolution
   • Verify NTP sync/server connection

[troglobit]

Tip: the DHCP server_subnets test case can be used for inspiration in this test.

[saba8814]

This has been resolved in #1410.