leafcn_max < target leafcn? parameter file leafcn_min and leafcn_max are on parameter files, but NOT used in the code, they are hardcoded to -10 and +15

It looks like the parameter leafcn_max is less than the target leafcn for some pfts? I don't yet understand how this effects simulations, but it doesn't look like the stoichiometry of other vegetation pools (livewdcn) has similar issues.

That said, the target C:N of live wood < leaves? This doesn't make sense?

### General bug information

**CTSM version you are using:** [output of `git describe`]
clm4518/n04/cime5.4.0-alpha.03

**Does this bug cause significantly incorrect results in the model's science?** [Yes / No]
Yes? But not yet tested.

**Configurations affected:** [Fill this in if known.]
default clm5 or any simulations with active bgc and flexCN

### Details of bug
ncdump -v leafcn,leafcn_min,leafcn_max,livewdcn /glade/p/cesmdata/cseg/inputdata/lnd/clm2/paramdata/clm5_params.c171117.nc

### Important details of your setup / configuration so we can reproduce the bug
to correct this, leafcn_min and leafcn_max should be +/- 10 from the target leafcn (as with livewdcn).
We'll need to do testing to see how this potentially changes answers.