DLPX-96941 Replace ntpsec with chrony (delphix-platform changes)

[manoj-joseph]

Background

The Delphix appliance previously used ntpsec as its NTP daemon (and before that, the legacy ntp package). Both packages are being replaced with chrony (DLPX-96940/96941/96942), motivated by two factors:

1. Security (DLPX-86999, Qualys QID 38293): ntpsec and ntp respond to NTP mode 6/7 queries, exposing sensitive system information (OS version, kernel, stratum, etc.) that can aid further attacks against the system. chrony does not support these query modes by default, eliminating the disclosure.
2. Ubuntu 25.04 compatibility: The Delphix Engine is planned to move to Ubuntu 25.04 later this year, where chrony is the default NTP daemon. Making this switch now avoids duplicating the migration effort at that time.

Companion PRs

This PR is part of a set of four that must merge together:

• dlpx-app-gate#4244 — app-stack changes
• This PR — platform changes
• appliance-build#857 — upgrade/migration scripts
• dlpx-qa-gate#8297 — QA gate test updates

Problem

The Delphix Engine's Debian package declared ntpsec as a dependency in debian/rules. This needs to be replaced with chrony.

Solution

One-line change in debian/rules: ntpsec replaced with chrony in the DEPENDS list.

Testing Done

Full appliance build including all three companion PRs verified on Jenkins:

Build	Description	Status
#13927	Full build + upgrade from 2025.3.0.1	UNSTABLE — dx-integration-tests: NtpServerMonitoringTest flakiness (fixed; see second set of runs below)
#13928	Full build + upgrade from 2025.6.0.0	SUCCESS
#13929	Full build + upgrade from 2026.2.0.0	UNSTABLE — upgrade-testing: pre-existing failure unrelated to this change
#13930	Full build	UNSTABLE — upgrade-testing: pre-existing failure unrelated to this change
#13941	Full build + upgrade from 2025.3.0.1	RUNNING
#13938	Full build + upgrade from 2025.6.0.0	RUNNING
#13940	Full build + upgrade from 2026.2.0.0	RUNNING
#13939	Full build	RUNNING

Note: The git workflow runs with only this repo's changes, without the companion changes in dlpx-app-gate#4244 and appliance-build#857. The appliance-build-orchestrator-pre-push runs pull in all three companion PRs together, so their results reflect the full end-to-end change.

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[prakashsurya]

I haven't fully reviewed test cases, etc.. so I'll rely on you to ensure that's comprehensive, etc.. otherwise, LGTM.