fixes to save on fractional save_steps

[winglian]

fixes #1642

per hf docs:

save_steps (int or float, optional, defaults to 500) — Number of updates steps before two checkpoint 
saves if save_strategy="steps". Should be an integer or a float in range [0,1). If smaller than 1, will be 
interpreted as ratio of total training steps.

but the hf trainer seems to have a regression where it doesn't properly save on fractional save_steps. This is a temporary workaround for now until this is fixed upstream.