Fix router closes client in case of hello timeout

[AdamLutka]

Solves goroutine leak in case of timeout of HELLO message from client.

Description, Motivation and Context

All other return statements with error in this function are called after method sendAbort that closes client. This PR adds close of client to last case that is missing.

What is the current behavior?

#242

What is the new behavior?

Client is closed after HELLO message timeout. This means that all goroutines of client end and memory can be collected.

What kind of change does this PR introduce?

• 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.
• I have added tests to cover my changes.
• Overall test coverage is not decreased.
• All new and existing tests passed.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.