Change django message storage backends default.
Change django message storage backends default.

Due to original cookie storage backends have limit 2048 bytes,
change it to fallbackstorage, which could store extra message in
session storage.

Related django storage illustration
https://docs.djangoproject.com/en/1.6/ref/contrib/messages/#module-django.contrib.messages

Closes-Bug: #1168541
Change-Id: Ieed4db962ccdadcb346c8ca7e6e789766f9838e5

blueboxgroup/horizon,endorphinl/horizon-fork,kfox1111/horizon,dan1/horizon-x509,blueboxgroup/horizon,RudoCris/horizon,xme1226/horizon,dan1/horizon-proto,redhat-cip/horizon,noironetworks/horizon,vladryk/horizon,gerrive/horizon,Mirantis/mos-horizon,pranavtendolkr/horizon,ChameleonCloud/horizon,BiznetGIO/horizon,NCI-Cloud/horizon,sandvine/horizon,dan1/horizon-x509,mandeepdhami/horizon,ChameleonCloud/horizon,liyitest/rr,wolverineav/horizon,doug-fish/horizon,openstack/horizon,liyitest/rr,RudoCris/horizon,redhat-cip/horizon,dan1/horizon-x509,mrunge/horizon_lib,damien-dg/horizon,agileblaze/OpenStackTwoFactorAuthentication,bac/horizon,tsufiev/horizon,newrocknj/horizon,NeCTAR-RC/horizon,anthonydillon/horizon,CiscoSystems/avos,ChameleonCloud/horizon,eayunstack/horizon,icloudrnd/automation_tools,RudoCris/horizon,anthonydillon/horizon,ging/horizon,mdavid/horizon,blueboxgroup/horizon,BiznetGIO/horizon,doug-fish/horizon,bac/horizon,tqtran7/horizon,BiznetGIO/horizon,icloudrnd/automation_tools,luhanhan/horizon,idjaw/horizon,dan1/horizon-proto,Mirantis/mos-horizon,agileblaze/OpenStackTwoFactorAuthentication,bigswitch/horizon,VaneCloud/horizon,vladryk/horizon,VaneCloud/horizon,Hodorable/0602,Metaswitch/horizon,henaras/horizon,damien-dg/horizon,noironetworks/horizon,karthik-suresh/horizon,mrunge/horizon_lib,Solinea/horizon,liyitest/rr,endorphinl/horizon-fork,bac/horizon,tsufiev/horizon,endorphinl/horizon-fork,mdavid/horizon,CiscoSystems/avos,saydulk/horizon,noironetworks/horizon,saydulk/horizon,endorphinl/horizon,gerrive/horizon,Dark-Hacker/horizon,orbitfp7/horizon,CiscoSystems/horizon,ging/horizon,tellesnobrega/horizon,mandeepdhami/horizon,orbitfp7/horizon,philoniare/horizon,nvoron23/avos,idjaw/horizon,luhanhan/horizon,yjxtogo/horizon,yjxtogo/horizon,CiscoSystems/horizon,luhanhan/horizon,VaneCloud/horizon,bigswitch/horizon,RudoCris/horizon,vladryk/horizon,tellesnobrega/horizon,davidcusatis/horizon,promptworks/horizon,endorphinl/horizon,anthonydillon/horizon,xinwu/horizon,tsufiev/horizon,agileblaze/OpenStackTwoFactorAuthentication,promptworks/horizon,orbitfp7/horizon,redhat-openstack/horizon,nvoron23/avos,tqtran7/horizon,newrocknj/horizon,j4/horizon,CiscoSystems/horizon,Solinea/horizon,FNST-OpenStack/horizon,endorphinl/horizon,pranavtendolkr/horizon,vladryk/horizon,karthik-suresh/horizon,maestro-hybrid-cloud/horizon,icloudrnd/automation_tools,Daniex/horizon,mrunge/horizon_lib,dan1/horizon-x509,henaras/horizon,watonyweng/horizon,promptworks/horizon,bac/horizon,FNST-OpenStack/horizon,django-leonardo/horizon,takeshineshiro/horizon,mandeepdhami/horizon,watonyweng/horizon,CiscoSystems/avos,davidcusatis/horizon,takeshineshiro/horizon,VaneCloud/horizon,henaras/horizon,ChameleonCloud/horizon,Dark-Hacker/horizon,wangxiangyu/horizon,yeming233/horizon,FNST-OpenStack/horizon,NCI-Cloud/horizon,icloudrnd/automation_tools,NeCTAR-RC/horizon,redhat-cip/horizon,Metaswitch/horizon,watonyweng/horizon,Metaswitch/horizon,coreycb/horizon,kfox1111/horizon,openstack/horizon,dan1/horizon-proto,bigswitch/horizon,kfox1111/horizon,coreycb/horizon,wangxiangyu/horizon,yjxtogo/horizon,django-leonardo/horizon,xme1226/horizon,NeCTAR-RC/horizon,j4/horizon,Daniex/horizon,FNST-OpenStack/horizon,luhanhan/horizon,saydulk/horizon,dan1/horizon-proto,Hodorable/0602,wolverineav/horizon,xinwu/horizon,nvoron23/avos,CiscoSystems/avos,karthik-suresh/horizon,yeming233/horizon,sandvine/horizon,liyitest/rr,Hodorable/0602,blueboxgroup/horizon,bigswitch/horizon,yeming233/horizon,mdavid/horizon,coreycb/horizon,yeming233/horizon,karthik-suresh/horizon,mandeepdhami/horizon,newrocknj/horizon,mdavid/horizon,Tesora/tesora-horizon,NCI-Cloud/horizon,maestro-hybrid-cloud/horizon,tqtran7/horizon,saydulk/horizon,Solinea/horizon,maestro-hybrid-cloud/horizon,sandvine/horizon,damien-dg/horizon,coreycb/horizon,CiscoSystems/horizon,xinwu/horizon,Tesora/tesora-horizon,redhat-openstack/horizon,NCI-Cloud/horizon,takeshineshiro/horizon,j4/horizon,izadorozhna/dashboard_integration_tests,openstack/horizon,philoniare/horizon,izadorozhna/dashboard_integration_tests,nvoron23/avos,pranavtendolkr/horizon,BiznetGIO/horizon,tellesnobrega/horizon,Mirantis/mos-horizon,pranavtendolkr/horizon,gerrive/horizon,anthonydillon/horizon,watonyweng/horizon,mrunge/openstack_horizon,orbitfp7/horizon,doug-fish/horizon,sandvine/horizon,ging/horizon,doug-fish/horizon,yjxtogo/horizon,wangxiangyu/horizon,redhat-cip/horizon,Dark-Hacker/horizon,maestro-hybrid-cloud/horizon,noironetworks/horizon,django-leonardo/horizon,ging/horizon,mrunge/openstack_horizon,Daniex/horizon,j4/horizon,django-leonardo/horizon,philoniare/horizon,henaras/horizon,kfox1111/horizon,agileblaze/OpenStackTwoFactorAuthentication,damien-dg/horizon,NeCTAR-RC/horizon,Solinea/horizon,wolverineav/horizon,tsufiev/horizon,xme1226/horizon,idjaw/horizon,redhat-openstack/horizon,idjaw/horizon,takeshineshiro/horizon,promptworks/horizon,philoniare/horizon,newrocknj/horizon,mrunge/openstack_horizon,davidcusatis/horizon,Tesora/tesora-horizon,tqtran7/horizon,Daniex/horizon,xinwu/horizon,endorphinl/horizon-fork,eayunstack/horizon,gerrive/horizon,openstack/horizon,eayunstack/horizon,redhat-openstack/horizon,Dark-Hacker/horizon,Hodorable/0602,tellesnobrega/horizon,wangxiangyu/horizon,Metaswitch/horizon,wolverineav/horizon,endorphinl/horizon,Mirantis/mos-horizon,Tesora/tesora-horizon,davidcusatis/horizon