Fix: sbd: Check if fence_sbd command exists before initializing device (bsc#1236184)

[liangxin1300]

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[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 69.74%. Comparing base (dddbde5) to head (47e3ba7).
Report is 9 commits behind head on master.

Files with missing lines	Patch %	Lines
crmsh/sbd.py	75.00%	1 Missing ⚠️

Additional details and impacted files

Flag	Coverage Δ
integration	53.54% <50.00%> (-0.03%)	⬇️
unit	53.10% <75.00%> (-0.01%)	⬇️

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Files with missing lines	Coverage Δ
crmsh/sbd.py	86.87% <75.00%> (-0.10%)	⬇️

... and 2 files with indirect coverage changes

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