[integr.test] Fix needless message while rm env.
[integr.test] Fix needless message while rm env.

If none environment is present and you trying to delete it, there should be
only one message about it. Now we test environment existance before using it.

nebril/fuel-web,teselkin/fuel-main,SmartInfrastructures/fuel-main-dev,stackforge/fuel-main,SergK/fuel-main,stackforge/fuel-web,dancn/fuel-main-dev,stackforge/fuel-main,Fiware/ops.Fuel-main-dev,prmtl/fuel-web,SmartInfrastructures/fuel-main-dev,dancn/fuel-main-dev,nebril/fuel-web,koder-ua/nailgun-fcert,Fiware/ops.Fuel-main-dev,huntxu/fuel-web,nebril/fuel-web,SergK/fuel-main,teselkin/fuel-main,prmtl/fuel-web,eayunstack/fuel-web,SmartInfrastructures/fuel-web-dev,koder-ua/nailgun-fcert,huntxu/fuel-main,SmartInfrastructures/fuel-main-dev,zhaochao/fuel-web,ddepaoli3/fuel-main-dev,stackforge/fuel-web,koder-ua/nailgun-fcert,dancn/fuel-main-dev,stackforge/fuel-web,huntxu/fuel-main,prmtl/fuel-web,eayunstack/fuel-main,prmtl/fuel-web,zhaochao/fuel-main,Fiware/ops.Fuel-main-dev,ddepaoli3/fuel-main-dev,huntxu/fuel-web,ddepaoli3/fuel-main-dev,AnselZhangGit/fuel-main,prmtl/fuel-web,huntxu/fuel-main,zhaochao/fuel-main,zhaochao/fuel-main,zhaochao/fuel-web,AnselZhangGit/fuel-main,AnselZhangGit/fuel-main,nebril/fuel-web,eayunstack/fuel-web,eayunstack/fuel-main,huntxu/fuel-web,dancn/fuel-main-dev,eayunstack/fuel-web,eayunstack/fuel-main,zhaochao/fuel-web,ddepaoli3/fuel-main-dev,zhaochao/fuel-web,eayunstack/fuel-web,stackforge/fuel-main,eayunstack/fuel-web,Fiware/ops.Fuel-main-dev,SmartInfrastructures/fuel-web-dev,zhaochao/fuel-main,zhaochao/fuel-main,AnselZhangGit/fuel-main,huntxu/fuel-web,teselkin/fuel-main,SmartInfrastructures/fuel-web-dev,koder-ua/nailgun-fcert,nebril/fuel-web,SmartInfrastructures/fuel-web-dev,SmartInfrastructures/fuel-main-dev,zhaochao/fuel-web,huntxu/fuel-web,teselkin/fuel-main,SergK/fuel-main,SmartInfrastructures/fuel-web-dev