New test in build-namelist_test.pl confirming no reseed on branch

Author: slevis-lmwg

bld/unit_testers/build-namelist_test.pl

@@ -678,6 +678,10 @@ sub cat_and_create_namelistinfile {
                                      namelst=>"soil_decomp_method='None'",
                                      phys=>"clm5_0",
                                    },
+     "reseed with branch"        =>{ options=>"-clm_start_type branch -envxml_dir .",
+                                     namelst=>"reseed_dead_plants=.true.",
+                                     phys=>"clm6_0",
+                                   },
      "reseed without CN"         =>{ options=>" -envxml_dir . -bgc sp",
                                      namelst=>"reseed_dead_plants=.true.",
                                      phys=>"clm5_0",