Refactor seconds_until_midnight_function #202
Description
...., the seconds_until_next_midnight may return an integer value -- but we can leave that for a later PR.
Originally posted by @hannesm in #200 (comment)
for context, seconds_until_midnight is used in our background checks if there are available unikernel updates. This background check should run everyday at midnight and the seconds_until_midnight function is used to determine how long we should wait.