IMPALA-1126: Remove strict unicode mode flag in shell

Removed the the --strict_unicode command-line option flag
because encoding to utf-8 is the same regardless if the
encoding policy is strict or ignore.

Change-Id: If71062d580072c51acb1bb401471ca818c97a9be
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/3725
Reviewed-by: Abdullah Yousufi <abdullah.yousufi@cloudera.com>
Tested-by: jenkins
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/4078