optimize the fallback code style

[zhangqiongyu]

What problem does this PR solve?

Issue Number:

Problem Summary:

What is changed and the side effects?

Changed: Engineering equivalent implementation, when I need to use multiple versions of ibverbs.so in actual applications, it is easier to expand. Side effects:

• Performance effects: no

• Breaking backward compatibility: no

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Check List:

• Please make sure your changes are compilable.
• When providing us with a new feature, it is best to add related tests.
• Please follow Contributor Covenant Code of Conduct.

[TousakaRin]

Does LD_LIBRARY_PATH meet your needs?

[zhangqiongyu]

Does LD_LIBRARY_PATH meet your needs?

yes，not only LD_LIBRARY_PATH but also soft link and renaming so can meet my needs. I just want to make this snippet more extensible.