Adding test cases for db package in SODA API

[nguptaopensds]

Issue/Feature Description:
Right now, api/db package has test coverage of 31.4%, we need to make it more than 60%. For that we need to add more test cases to the package.

Why this issue to fixed / feature is needed(give scenarios or use cases):
Quality improvement is integral part of any project and to reach that we need to achieve test coverage of more than 60%

How to reproduce, in case of a bug:

Other Notes / Environment Information: (Please give the env information, log link or any useful information for this issue)

[nguptaopensds]

Parent issue : #1268