Be stricter in durations that are accepted. Basically we accept ISO 8601
formats, but fail to detect garbage after the integers in such strings.
For example, 'P7.5D' will be treated as 7 days. Pass 'endptr' to
'strtoll' and check if the endptr is at the correct suffix.
(cherry picked from commit e39de45adc)
a621e035d4