fix(uiSelectCtrl): Reset refreshing flag even if async request errors
fix(uiSelectCtrl): Reset refreshing flag even if async request errors

Previously the `ctrl.refreshing` flag may not have been reset to `false` if the async request for data failed. 

Closes #1833 
Crunch-io/ui-select,Jefiozie/ui-select,ivanvoznyakovsky/ui-select,granteagon/ui-select-temp,Servoy/ui-select,Jefiozie/ui-select,Crunch-io/ui-select,angular-ui/ui-select,ivanvoznyakovsky/ui-select,billypon/ui-select,looker/ui-select,Jefiozie/ui-select,MartinDeHaan/ui-select-submitform,Jobularity/ui-select,looker/ui-select,looker/ui-select,Jobularity/ui-select,granteagon/ui-select-temp,ivanvoznyakovsky/ui-select,MartinDeHaan/ui-select-submitform,Jobularity/ui-select,angular-ui/ui-select,Servoy/ui-select,MartinDeHaan/ui-select-submitform,angular-ui/ui-select,billypon/ui-select,Crunch-io/ui-select,granteagon/ui-select-temp,billypon/ui-select,Servoy/ui-select