[Contrail 4.0] Plugin tests did not pass shellcheck

Scenario:
  1. Install shellcheck
  2.Run shellcheck for plugin_test/utils/jenkins/system_tests.sh

Actual result:
  yshapovalov@yshapovalov-pc:~/fuel-plugin-contrail$ shellcheck plugin_test/utils/jenkins/system_tests.sh

In plugin_test/utils/jenkins/system_tests.sh line 26:
if [ -z $NODE_VOLUME_SIZE ]; then export NODE_VOLUME_SIZE=350; fi
        ^-- SC2086: Double quote to prevent globbing and word splitting.

In plugin_test/utils/jenkins/system_tests.sh line 27:
if [ -z $OPENSTACK_RELEASE ]; then export OPENSTACK_RELEASE=Ubuntu; fi
        ^-- SC2086: Double quote to prevent globbing and word splitting.

In plugin_test/utils/jenkins/system_tests.sh line 28:
if [ -z $ENV_NAME ]; then export ENV_NAME="contrail"; fi
        ^-- SC2086: Double quote to prevent globbing and word splitting.

In plugin_test/utils/jenkins/system_tests.sh line 29:
if [ -z $ADMIN_NODE_MEMORY ]; then export ADMIN_NODE_MEMORY=4096; fi
        ^-- SC2086: Double quote to prevent globbing and word splitting.

In plugin_test/utils/jenkins/system_tests.sh line 30:
if [ -z $ADMIN_NODE_CPU ]; then export ADMIN_NODE_CPU=4; fi
        ^-- SC2086: Double quote to prevent globbing and word splitting.

In plugin_test/utils/jenkins/system_tests.sh line 31:
if [ -z $SLAVE_NODE_MEMORY ]; then export SLAVE_NODE_MEMORY=4096; fi
        ^-- SC2086: Double quote to prevent globbing and word splitting.

In plugin_test/utils/jenkins/system_tests.sh line 32:
if [ -z $SLAVE_NODE_CPU ]; then export SLAVE_NODE_CPU=4; fi
        ^-- SC2086: Double quote to prevent globbing and word splitting.

In plugin_test/utils/jenkins/system_tests.sh line 284:
    ISO="`ls ${WORKSPACE}/build/iso/*.iso | head -n 1`"
         ^-- SC2006: Use $(..) instead of deprecated `..`
          ^-- SC2012: Use find instead of ls to better handle non-alphanumeric filenames.
             ^-- SC2086: Double quote to prevent globbing and word splitting.

In plugin_test/utils/jenkins/system_tests.sh line 372:
                echo wget -c ${ISO_URL} -O ${ISO_PATH}
                             ^-- SC2086: Double quote to prevent globbing and word splitting.
                                           ^-- SC2086: Double quote to prevent globbing and word splitting.

In plugin_test/utils/jenkins/system_tests.sh line 375:
                wget -c ${ISO_URL} -O ${ISO_PATH}
                        ^-- SC2086: Double quote to prevent globbing and word splitting.
                                      ^-- SC2086: Double quote to prevent globbing and word splitting.

In plugin_test/utils/jenkins/system_tests.sh line 407:
      mkdir -p $LOGS_DIR
               ^-- SC2086: Double quote to prevent globbing and word splitting.

In plugin_test/utils/jenkins/system_tests.sh line 419:
        if [ $(dos.py list | grep "^${ENV_NAME}\$") ]; then
             ^-- SC2046: Quote this to prevent word splitting.
             ^-- SC2143: Instead of [ -n $(foo | grep bar) ], use foo | grep -q bar .

In plugin_test/utils/jenkins/system_tests.sh line 440:
        echo python plugin_test/run_tests.py -q --nologcapture --with-xunit ${OPTS}
                                                                            ^-- SC2086: Double quote to prevent globbing and word splitting.

In plugin_test/utils/jenkins/system_tests.sh line 443:
        echo ${PYTHONPATH}
             ^-- SC2086: Double quote to prevent globbing and word splitting.

In plugin_test/utils/jenkins/system_tests.sh line 444:
        python plugin_test/run_tests.py -q --nologcapture --with-xunit ${OPTS}
                                                                       ^-- SC2086: Double quote to prevent globbing and word splitting.

In plugin_test/utils/jenkins/system_tests.sh line 484:
GetoptsVariables ${@}
                 ^-- SC2068: Double quote array expansions, otherwise they're like $* and break on spaces.