cluster: fix custom port handling for drainer on importing

[AstroProfundis]

What problem does this PR solve?

The custom drainer_port for host is not read on import, so the value in group_vars is used instead.

Check List

Tests

• Unit test

Code changes

• Has persistent data change

Side effects

• None

Related changes

• Need to cherry-pick to the release branch

Release notes:

Fix per-host custom port for drainer not handled correctly on importing

[codecov-commenter]

Codecov Report

Merging #806 into master will decrease coverage by 2.61%.
The diff coverage is 33.33%.

@@            Coverage Diff             @@
##           master     #806      +/-   ##
==========================================
- Coverage   51.32%   48.70%   -2.62%     
==========================================
  Files         262      262              
  Lines       18844    18850       +6     
==========================================
- Hits         9671     9181     -490     
- Misses       7629     8210     +581     
+ Partials     1544     1459      -85     

Flag	Coverage Δ
#cluster	39.09% <0.00%> (-3.36%)	⬇️
#dm	25.33% <0.00%> (-0.08%)	⬇️
#integrate	43.82% <0.00%> (-2.26%)	⬇️
#playground	22.22% <ø> (ø)
#tiup	10.93% <ø> (ø)
#unittest	18.56% <33.33%> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
pkg/cluster/ansible/service.go	3.64% <0.00%> (ø)
pkg/cluster/ansible/inventory.go	54.16% <100.00%> (+0.94%)	⬆️
components/cluster/command/check.go	6.39% <0.00%> (-72.73%)	⬇️
pkg/cluster/task/limits.go	0.00% <0.00%> (-68.75%)	⬇️
pkg/cluster/task/sysctl.go	0.00% <0.00%> (-66.67%)	⬇️
components/cluster/command/audit.go	27.27% <0.00%> (-54.55%)	⬇️
pkg/cluster/operation/check.go	0.00% <0.00%> (-51.95%)	⬇️
pkg/cluster/task/rmdir.go	0.00% <0.00%> (-50.00%)	⬇️
pkg/cluster/operation/operation.go	34.78% <0.00%> (-43.48%)	⬇️
components/cluster/command/rename.go	25.00% <0.00%> (-41.67%)	⬇️
... and 42 more

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[lonng]

LGTM