fix(redis): pipe cannot take err except for pipe.Exec

[MaineK00n]

What did you implement:

Since pipe can't get err except for pipe.Exec, I modified the code.

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Checklist:

You don't have to satisfy all of the following.

• Write tests
• Write documentation
• Check that there aren't other open pull requests for the same issue/feature
• Format your source code by make fmt
• Pass the test by make test
• Provide verification config / commands
• Enable "Allow edits from maintainers" for this PR
• Update the messages below

Is this ready for review?: YES

Reference

[kotakanbe]

LGTM