Merge branch 'darincomeau/ocn/change-conservation-clobber' into next …

…(PR #6258)

Changing clobber mode in ocean conservation analysis

Previously the clobber mode in the ocean conservation analysis member
was set to 'append', which would throw errors to log.ocean.*.err files
when rerunning a case.

Changing clobber mode to truncate avoids these errors.

[BFB]

components/mpas-ocean/cime_config/buildnml

@@ -1006,7 +1006,7 @@ def buildnml(case, caseroot, compname):
             lines.append('        filename_interval="00-01-00_00:00:00"')
             lines.append('        reference_time="01-01-01_00:00:00"')
             lines.append('        output_interval="00-01-00_00:00:00"')
-            lines.append('        clobber_mode="append"')
+            lines.append('        clobber_mode="truncate"')
             lines.append('        packages="conservationCheckAMPKG">')
             lines.append('')
             lines.append('<var name="xtime"/>')