Partitioning on boot sometimes aborts because of partprobe failing

We received a WB report (da054cb0246450ddda6657a8a9999d70) about a failure on second boot.

Apprently due to the execution of partprobe from init-premount script.

Feature Branch: bugfix/16731-explicit-partprobe

Original created by @mercedes508 on 16731 (Redmine)

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