Resolve "Vet testing in `util/factory`"

General MR

Summary

Increase the code coverage for BBCTL util/factory and ensure existing tests provide proper tests of the functionality.

Relevant logs/screenshots

Increases the test coverage of util/factory from 44.8% on the main branch to 100% on the feature branch:

bbctl (main) ✗ go test ./util -v --coverprofile=cover.txt
...
--- PASS: TestGetCommandExecutorBadConfig (0.00s)
PASS
coverage: 44.8% of statements
ok  	repo1.dso.mil/big-bang/product/packages/bbctl/util	0.750s	coverage: 44.8% of statements

vs.

bbctl (74-vet-testing-in-util-factory) ✗ go test ./util -v --coverprofile=cover.txt
...
    --- PASS: TestGetRuntimeClient/WithErrorScheme (0.00s)
PASS
coverage: 100.0% of statements
ok  	repo1.dso.mil/big-bang/product/packages/bbctl/util	1.579s	coverage: 100.0% of statements

Linked Issue

#74 (closed)

Upgrade Notices

N/A

Closes #74 (closed)