IMPALA-4636: Correct Suse Linux distro string
IMPALA-4636: Correct Suse Linux distro string

The string should be suselinux12, not sles12.

I tested this by sourcing the config script on a SLES12 SP1 instance.
Before the change, KUDU_IS_SUPPORTED == false. With the change, the
value is set to true.

Change-Id: I28897eb4e0bbac77e1e542c3db4834a987348f7a
Reviewed-on: http://gerrit.cloudera.org:8080/5519
Reviewed-by: Jim Apple <396f577ccd0f19e47f0fb44dae1d6fc43cc20400@apache.org>
Reviewed-by: Michael Brown <97e4d5d0e400e5ad37382425ea95bde8b3933403@cloudera.com>
Tested-by: Impala Public Jenkins

michaelhkw/incubator-impala,michaelhkw/incubator-impala,michaelhkw/incubator-impala,michaelhkw/incubator-impala,cloudera/Impala,cloudera/Impala,cloudera/Impala,cloudera/Impala,michaelhkw/incubator-impala,cloudera/Impala,michaelhkw/incubator-impala,cloudera/Impala,cloudera/Impala,michaelhkw/incubator-impala