[services] Tunnelbroker - Tools tests

Summary:
Tools - is an internal toolset of functions.

We perform tests on such functions:

• generateRandomString(),
• validateDeviceID(),
• validateSessionID().

Test Plan: Run yarn test-tunnelbroker-service all tests are run and succeed.

Reviewers: karol-bisztyga, palys-swm, varun

Reviewed By: karol-bisztyga, palys-swm

Subscribers: ashoat, palys-swm, Adrian, atul, karol-bisztyga, benschac, yayabosh

Differential Revision: https://phabricator.ashoat.com/D3654