feat: Enable NTP on iDRAC, and stop using Ironic's verify_bmc_clock

[stevekeay]

We need proper time syncronisation on the iDRAC for:

(1) SSL connections made by the iDRAC to download firmware updates (2) When using SSO/DEX authentication

Here we choose NTP as the way to sync the time.

The IPA image has a clock-step functionality but it does not always work, and when it fails it causes IPA to fail altogether.

When NTP is enabled, the time-of-day redfish route becomes read-only and IPA will fail 100% of the time - these two methods are mutually exclusive, so we disable the IPA's clock-setting mechanism.

We might want to proactively update the drac configurations. This could be done quite cheaply with some kind of one-liner like:

export NTP_SERVER_IPV4_ADDR_1=10.4.91.240 # note: varies per data center
export NTP_SERVER_IPV4_ADDR_2=10.4.91.241 # note: varies per data center

uv run python -c "from understack_workflows import bmc, bmc_settings; print(bmc_settings.update_dell_drac_settings(bmc.bmc_for_ip_address('$drac_ip')))"