The compute manager code that uses the
block_device_allocate_retries option was handling
values less than zero, logging a warning and treating
the value as 0. This change removes that code and just
sets min=0 on the option itself. A release note is added
for the potential upgrade impact.
Change-Id: Ia5b99f7c96a8b6bce6899a6ff04019ab65487db9
Closes-Bug: #1819049