[spark] Replace bad Guava import

TestImportExportFiles uses the shaded Spark import of
ImmutableList. Instead we should use the actual Guava import.

Change-Id: Id75b16ad80800df554cfd129a70c03d9250e2292
Reviewed-on: http://gerrit.cloudera.org:8080/15084
Tested-by: Kudu Jenkins
Reviewed-by: Andrew Wong <awong@cloudera.com>
Reviewed-by: Bankim Bhavsar <bankim@cloudera.com>
1 file changed