Simplify loop and fix off-by-one error with unneeded sleep

When this loop is executed, its counter goes from max_attempts, let's say 3 to 0
(2, 1, 0). Before each try of resending message were entered sleep, to not send
all retries in almost same moment. So expected behavior was:
- first try (2 attempts left, previously were 3)
- failed, so sleep...
- second try (1 attempts left, previously were 2)
- failed, so sleep...
- third try (0 attempts left, previously were 1)
- failed, but there is no more attempts left (previously was 1), so immediately
  raise exception, without sleep.

Previous code version, because of bug, unnecessary waited before raising exception.