IMPALA-2460: randomize table names in TestParquetArrayEncodings
IMPALA-2460: randomize table names in TestParquetArrayEncodings

The exhaustive build will run multiple instances of the same test
within a single DB, so we need unique tablenames since we don't drop
the tables when each test finishes.

Change-Id: I4a5895d872513d7b7debcbf9cafbeeed5c8819f7
Reviewed-on: http://gerrit.cloudera.org:8080/1130
Reviewed-by: Dan Hecht <20ebd99959f0f6e5dcb0fc319b4d8ef53a16b5fb@cloudera.com>
Tested-by: Dan Hecht <20ebd99959f0f6e5dcb0fc319b4d8ef53a16b5fb@cloudera.com>

ibmsoe/ImpalaPPC,ibmsoe/ImpalaPPC,ibmsoe/ImpalaPPC,ibmsoe/ImpalaPPC,ibmsoe/ImpalaPPC,ibmsoe/ImpalaPPC,ibmsoe/ImpalaPPC