Attribute Clients is used if it is set

[sidey79]

• Please check if the PR fulfills these requirements

• Tests for the changes have been added / modified (needed for for bug fixes / features)
• commandref has been added / updated (needed for bug fixes / features)

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

• Bugfix (please link issue)
• Feature enhancement
• Documentation update
• Unittest enhancement
• other

• What is the current behavior?
  (You can also link to an open issue here, if this describes the current behavior)

#1264

• What is the new behavior (if this is a feature change)?

Setting the Clients attribute uses the selected values if it evaluates to true.
Otherwise defaults are used.

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)

no

• Other information:

[codecov]

Codecov Report

Attention: Patch coverage is 94.73684% with 1 line in your changes missing coverage. Please review.

Project coverage is 70.95%. Comparing base (c940a2d) to head (be31bfc).
Report is 6 commits behind head on master.

Files with missing lines	Patch %	Lines
FHEM/00_SIGNALduino.pm	66.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1266      +/-   ##
==========================================
- Coverage   71.53%   70.95%   -0.58%     
==========================================
  Files         138      137       -1     
  Lines       10215    10226      +11     
  Branches     1602     1602              
==========================================
- Hits         7307     7256      -51     
- Misses       1575     1636      +61     
- Partials     1333     1334       +1     

Flag	Coverage Δ
fhem	61.63% <94.73%> (-0.67%)	⬇️
modules	70.95% <94.73%> (-0.58%)	⬇️
perl	88.92% <ø> (ø)
unittests	70.95% <94.73%> (-0.58%)	⬇️

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