storage: Refactor virStorageBackendFileSystemGetPoolSource
storage: Refactor virStorageBackendFileSystemGetPoolSource

Refactor code to use standard return functioning with respect to setting
a ret value and going to cleanup.

jardasgit/libvirt,crobinso/libvirt,olafhering/libvirt,rlaager/libvirt,datto/libvirt,fabianfreyer/libvirt,zippy2/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,olafhering/libvirt,eskultety/libvirt,fabianfreyer/libvirt,rlaager/libvirt,libvirt/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,zippy2/libvirt,rlaager/libvirt,andreabolognani/libvirt,jfehlig/libvirt,nertpinx/libvirt,eskultety/libvirt,VenkatDatta/libvirt,libvirt/libvirt,andreabolognani/libvirt,olafhering/libvirt,jfehlig/libvirt,andreabolognani/libvirt,jardasgit/libvirt,zippy2/libvirt,libvirt/libvirt,crobinso/libvirt,taget/libvirt,jardasgit/libvirt,nertpinx/libvirt,zippy2/libvirt,eskultety/libvirt,rlaager/libvirt,libvirt/libvirt,VenkatDatta/libvirt,datto/libvirt,crobinso/libvirt,taget/libvirt,fabianfreyer/libvirt,taget/libvirt,datto/libvirt,eskultety/libvirt,nertpinx/libvirt,datto/libvirt,jardasgit/libvirt,eskultety/libvirt,VenkatDatta/libvirt,nertpinx/libvirt,taget/libvirt,olafhering/libvirt,jardasgit/libvirt,rlaager/libvirt,datto/libvirt,nertpinx/libvirt,VenkatDatta/libvirt,andreabolognani/libvirt,andreabolognani/libvirt,taget/libvirt,VenkatDatta/libvirt,crobinso/libvirt