v.rast.stats: fix handling column prefixes (merge from trunk, https://trac.osgeo.org/grass/changeset/66864)

git-svn-id: https://svn.osgeo.org/grass/grass/branches/releasebranch_7_0@67033 15284696-431f-4ddb-bdfa-cd5b030d7da7

scripts/v.rast.stats/v.rast.stats.py

@@ -262,7 +262,7 @@ def main():
         f.write("UPDATE %s SET" % fi['table'])
         first_var = 1
         for colname in colnames:
-            variable = colname.replace("%s_" % colprefix, '')
+            variable = colname.replace("%s_" % colprefix, '', 1)
             if dbfdriver:
                 variable = variables_dbf[variable]
             i = variables[variable]