fix undesired debug statement printing

[jseagrave21]

What current issue(s) does this address, or what feature is it adding?

• resubmitting https://github.com/ixje/neo-python/pull/17
• addresses [alpha2] move from twisted to asyncio + new network #934 (comment)

How did you solve this problem?

• searched for logzero imports
• replaced with log_manager where necessary: Transaction.py & Send.py
• completed manual testing to verify expected result

How did you make sure your solution works?
manual testing

NOTE: I don't think I can add individual unittests for this issue because running make test displays every level of logger.

Are there any special changes in the code that we should be aware of?
no

Please check the following, if applicable:

• Did you add any tests?
• Did you run make lint?
• Did you run make test?
• Are you making a PR to a feature branch or development rather than master?
• Did you add an entry to CHANGELOG.rst? (if not, please do)

[coveralls]

Coverage increased (+0.001%) to 85.052% when pulling 0893489 on jseagrave21:rm-logzero-2 into c95fec6 on CityOfZion:development.

[ixje]

thanks!