logout() fucntion added and isSessionIdExists() removed.

[grvgoel81]

Motivation and Context

• logout() function added.
• isSessionIdExists function modified.

Jira Link: https://toruslabs.atlassian.net/browse/PD-3917

Description

• logout() function added.
• isSessionIdExists function modified.

How has this been tested?

• By running all unit tests.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project. (run lint)
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[metalurgical]

Included in #24