Guard against oversize flavor rxtx_factor float

We now check that rxtx_factor provided is not greater than
the Float type to be stored in the db. While the check is not
100% accurate due to float approximation it will be very
close to the max allowable. A 400 error is returned if the
provided value is too big.

Closes-Bug: 1259213
Change-Id: I72c52fa46d75275c45e72b6f5a36106d5abf8220
Co-authored-by: Takashi Natsume <natsume.takashi@lab.ntt.co.jp>
Enable flake8 H404 checking

This check indicates on comments in which multi line docstring should
start without a leading new line. This change fixed all violators of
said check.

Change-Id: Ic7357b8c7420767dba611f6fcee07b7700f3aea8
Merge "Enable flake8 H404 checking"
Merge "Guard against oversize flavor rxtx_factor float"