Minion pillar manager trigger refresh after update

[sandonovsuse]

What does this PR change?

Triggers pillar data refresh. Targeting a salt-minion via CLI by a group newly joined using GUI fails without refreshing pillar data first.

GUI diff

No difference.

• [x] DONE

Documentation

• No documentation needed: Bugfix
• [x] DONE

Test coverage

• No tests: already covered
• [x] DONE

Links

Tracks SUSE/spacewalk#17420

• [x] DONE

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