Fix android issues for stopping and restarting training

[nvkevlu]

Fixes issues with connection closing and reporting the stopping of training to the server so it can be smoothly started again.

Types of changes

• Non-breaking change (fix or new feature that would not break existing functionality).
• Breaking change (fix or new feature that would cause existing functionality to change).
• New tests added to cover the changes.
• Quick tests passed locally by running ./runtest.sh.
• In-line docstrings updated.
• Documentation updated.

[chesterxgchen]

@nvkevlu is this PR going to the current release ?

[nvkevlu]

There may be additional changes to this, and to ensure to not break any existing functionality, it may be safer for these changes to go into the next release.