remote_driver: don't fail if keepalive check fails
remote_driver: don't fail if keepalive check fails

Otherwise connections to older libvirt abort with:

$ virsh -c qemu+ssh://host.example.com/system list
error: invalid connection pointer in virDrvSupportsFeature
error: failed to connect to the hypervisor

Tested against 0.8.3 and 0.9.8-rc2.

rmarwaha/libvirt,danwent/libvirt-ovs,warewolf/libvirt,iam-TJ/libvirt,cbosdo/libvirt,fabianfreyer/libvirt,jeckersb/libvirt,nertpinx/libvirt,rlaager/libvirt,novel/fbsd-libvirt,siboulet/libvirt-openvz,rmarwaha/libvirt,danwent/libvirt-ovs,rmarwaha/libvirt1,wiedi/libvirt,foomango/libvirt,trainstack/libvirt,jardasgit/libvirt,nertpinx/libvirt,olafhering/libvirt,iam-TJ/libvirt,eskultety/libvirt,siboulet/libvirt-openvz,zhlcindy/libvirt-1.1.4-maintain,VenkatDatta/libvirt,olafhering/libvirt,zippy2/libvirt,novel/fbsd-libvirt,zippy2/libvirt,warewolf/libvirt,taget/libvirt,jardasgit/libvirt,taget/libvirt,jfehlig/libvirt,jardasgit/libvirt,nertpinx/libvirt,VenkatDatta/libvirt,wiedi/libvirt,shugaoye/libvirt,VenkatDatta/libvirt,shugaoye/libvirt,siboulet/libvirt-openvz,cbosdo/libvirt,fabianfreyer/libvirt,bjzhang/libvirt,novel/fbsd-libvirt,warewolf/libvirt,taget/libvirt,wiedi/libvirt,agx/libvirt,jeckersb/libvirt,dumbbell/libvirt,eskultety/libvirt,dumbbell/libvirt,dumbbell/libvirt,taget/libvirt,nertpinx/libvirt,crobinso/libvirt,eskultety/libvirt,datto/libvirt,datto/libvirt,datto/libvirt,warewolf/libvirt,warewolf/libvirt,agx/libvirt,jfehlig/libvirt,elmarco/libvirt,warewolf/libvirt,nertpinx/libvirt,rmarwaha/libvirt,crobinso/libvirt,trainstack/libvirt,rmarwaha/libvirt,dumbbell/libvirt,wiedi/libvirt,rmarwaha/libvirt1,libvirt/libvirt,libvirt/libvirt,bjzhang/libvirt,novel/fbsd-libvirt,bjzhang/libvirt,wiedi/libvirt,emaste/libvirt,shugaoye/libvirt,zhlcindy/libvirt-1.1.4-maintain,zhlcindy/libvirt-1.1.4-maintain,jfehlig/libvirt,dumbbell/libvirt,jeckersb/libvirt,rmarwaha/libvirt1,agx/libvirt,libvirt/libvirt,VenkatDatta/libvirt,warewolf/libvirt,emaste/libvirt,novel/fbsd-libvirt,danwent/libvirt-ovs,trainstack/libvirt,agx/libvirt,siboulet/libvirt-openvz,taget/libvirt,trainstack/libvirt,trainstack/libvirt,emaste/libvirt,jeckersb/libvirt,datto/libvirt,wiedi/libvirt,trainstack/libvirt,datto/libvirt,elmarco/libvirt,trainstack/libvirt,iam-TJ/libvirt,dumbbell/libvirt,andreabolognani/libvirt,jardasgit/libvirt,rmarwaha/libvirt,libvirt/libvirt,cbosdo/libvirt,bjzhang/libvirt,agx/libvirt,zhlcindy/libvirt-1.1.4-maintain,iam-TJ/libvirt,shugaoye/libvirt,siboulet/libvirt-openvz,cbosdo/libvirt,foomango/libvirt,rmarwaha/libvirt1,wiedi/libvirt,foomango/libvirt,rmarwaha/libvirt1,emaste/libvirt,iam-TJ/libvirt,shugaoye/libvirt,emaste/libvirt,zippy2/libvirt,iam-TJ/libvirt,foomango/libvirt,jeckersb/libvirt,novel/fbsd-libvirt,rlaager/libvirt,andreabolognani/libvirt,zhlcindy/libvirt-1.1.4-maintain,elmarco/libvirt,fabianfreyer/libvirt,jeckersb/libvirt,elmarco/libvirt,crobinso/libvirt,iam-TJ/libvirt,fabianfreyer/libvirt,fabianfreyer/libvirt,crobinso/libvirt,rlaager/libvirt,eskultety/libvirt,emaste/libvirt,novel/fbsd-libvirt,zippy2/libvirt,rlaager/libvirt,danwent/libvirt-ovs,elmarco/libvirt,olafhering/libvirt,jardasgit/libvirt,andreabolognani/libvirt,danwent/libvirt-ovs,novel/fbsd-libvirt,bjzhang/libvirt,jeckersb/libvirt,eskultety/libvirt,andreabolognani/libvirt,olafhering/libvirt,rlaager/libvirt,VenkatDatta/libvirt,rmarwaha/libvirt1,cbosdo/libvirt,foomango/libvirt,emaste/libvirt,novel/fbsd-libvirt,jfehlig/libvirt,rmarwaha/libvirt,andreabolognani/libvirt