mizuRoute NUOPC cap only allows running with a daily or more coupling period

Currently the NUOPC cap gets the coupling period in days as an integer, which means trying to run subdaily ends up with 0 which is disallowed.

@nmizukami and I looked at this together, and the call to ESMF_TimeIntervalGet just needs to change from

d=coupling_period

to

s=coupling_period

And we may use s_r8 instead to return a double precision value. Which would work in the code easier.