Remove duplicate import_str in java_import command

Change,

commit 5411cb545d18cb8c74610531c1cf2fa704d67751
Author: Barthelemy Dagenais <bart@cs.mcgill.ca>
Date:   Sat Mar 12 13:08:27 2011 -0500
    initial work on supporting byte[] and cleaning unicode treatment...

appears to have duplicated the import_str sent to the server during
java_import. The duplication does not cause a fatal error or incorrect
behavior, but does generate a warning from the server about unknown
commands.

For instance, java_import(..., "org.apache.spark.SparkConf") results
in,

   Command to send: j
   i
   rj
   org.apache.spark.SparkConf
   e

   org.apache.spark.SparkConf
   e

and,

   py4j.GatewayConnection run
   WARNING: Unknown command
   py4j.GatewayConnection run
   WARNING: Unknown command org.apache.spark.SparkConf
   py4j.GatewayConnection run
   WARNING: Unknown command e
Merge pull request #143 from mattf/master-0

Remove duplicate import_str in java_import command