Merge branch 'jonbob/tools/reset-fminval-gen-domain' into next (PR #7466)

Set default value of fminval in python version of gen_domain to 1.0e-08

The current version of gen_domain has a default value of 0.001 for the
min allowable land fraction. That is too large and shows up in the cpl
area budget for e3sm runs. The fminval can be overwritten on the command
line but rarely is, so it seems safer to make the default much smaller
(1e-8) instead. The resulting domain files will have a different number
of lnd cells, so it would be complicated to regenerate domain files for
all supported mesh configurations. But at least any new domain files
should be corrected.

Partially fixes #7465 -- the Fortran version in CIME also has the same
                         issue
[non-BFB] for any new domain files

Author: jonbob

tools/generate_domain_files/generate_domain_files_E3SM.py

@@ -94,7 +94,7 @@ class clr:END,RED,GREEN,MAGENTA,CYAN = '\033[0m','\033[31m','\033[32m','\033[35m
                   help='Creation date stamp for domain files')
 parser.add_option('--fminval',
                   dest='fminval',
-                  default=1e-3,
+                  default=1e-8,
                   help='Minimum allowable land fraction (reset to 0 below fminval)')
 parser.add_option('--fmaxval',
                   dest='fmaxval',