Add unit tests for Blind Sql Injection Vulnerability

[preetkaran20]

Is your feature request related to a problem? Please describe. We are looking at increasing the Test coverage for the project for its stability so this task is to add junit tests for https://github.com/SasanLabs/VulnerableApp/blob/master/src/main/java/org/sasanlabs/service/vulnerability/sqlInjection/BlindSQLInjectionVulnerability.java

[preetkaran20]

Parent issue: https://github.com/SasanLabs/VulnerableApp/issues/212