fix(sysfs): add check for empty devpath

[akhilerm]

Signed-off-by: Akhil Mohan akhil.mohan@mayadata.io

Why is this PR required? What issue does it fix?:
If the devpath received due to some error is empty, then sysfs device creation caused a crash. This PR adds a check for empty path before creating a sysfs device.

What this PR does?:

• adds check for empty device path

Does this PR require any upgrade changes?:
No

If the changes in this PR are manually verified, list down the scenarios covered::

Any additional information for your reviewer? :
Mention if this PR is part of any design or a continuation of previous PRs

Checklist:

• Fixes openebs-ndm crashing on restart after block device resize openebs/openebs#3362
• PR Title follows the convention of <type>(<scope>): <subject>
• Has the change log section been updated?
• Commit has unit tests
• Commit has integration tests
• (Optional) Are upgrade changes included in this PR? If not, mention the issue/PR to track:
• (Optional) If documentation changes are required, which issue on https://github.com/openebs/openebs-docs is used to track them:

[codecov-io]

Codecov Report

Merging #560 (7fe55e9) into master (ef2bb97) will decrease coverage by 0.86%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master     #560      +/-   ##
==========================================
- Coverage   49.39%   48.52%   -0.87%     
==========================================
  Files          73       73              
  Lines        3365     3367       +2     
==========================================
- Hits         1662     1634      -28     
- Misses       1548     1578      +30     
  Partials      155      155              

Impacted Files	Coverage Δ
pkg/sysfs/device.go	27.27% <66.66%> (+27.27%)	⬆️
cmd/ndm_daemonset/probe/eventhandler.go	40.00% <0.00%> (-10.91%)	⬇️
cmd/ndm_daemonset/probe/addhandler.go	71.13% <0.00%> (-6.19%)	⬇️
cmd/ndm_daemonset/probe/udevprobe.go	63.12% <0.00%> (-3.92%)	⬇️

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