IMPALA-1040: Reading a decimal partitioned column with invalid values

This commit fixes IMPALA-1040 in which when an invalid value is inserted
to a decimal partitioned column through hive it results in a non
informative error message and in some cases in the associated table to
disappear from Impala's catalog. The fix results in a more informative
error message to always be thrown by Impala to indicate the insertion of
an invalid partition key value.

Change-Id: I2855ea69944e269fb7e02b3825f44e64352151e7
Reviewed-on: http://gerrit.ent.cloudera.com:8080/3062
Reviewed-by: Dimitris Tsirogiannis <dtsirogiannis@cloudera.com>
Tested-by: jenkins