qemuDomainBlockCommit: Move checks depending on capabilities after liveness check
qemuDomainBlockCommit: Move checks depending on capabilities after liveness check

Since capabilities are not present for inactive VMs we'd report that we
don't support '--delete' or committing while checkpoints exist rather
than the proper error.

Signed-off-by: Peter Krempa <2cf5c04c61aa466e4a47bfedc747d17279c72ffc@redhat.com>
Reviewed-by: Eric Blake <a9da18479c871fe903d9590822cfe2629c6a4d11@redhat.com>

fabianfreyer/libvirt,crobinso/libvirt,fabianfreyer/libvirt,olafhering/libvirt,crobinso/libvirt,nertpinx/libvirt,jfehlig/libvirt,olafhering/libvirt,libvirt/libvirt,jardasgit/libvirt,zippy2/libvirt,zippy2/libvirt,jfehlig/libvirt,libvirt/libvirt,zippy2/libvirt,zippy2/libvirt,nertpinx/libvirt,jfehlig/libvirt,libvirt/libvirt,fabianfreyer/libvirt,crobinso/libvirt,libvirt/libvirt,jardasgit/libvirt,olafhering/libvirt,jardasgit/libvirt,crobinso/libvirt,nertpinx/libvirt,fabianfreyer/libvirt,olafhering/libvirt,jfehlig/libvirt,nertpinx/libvirt,jardasgit/libvirt,jardasgit/libvirt,nertpinx/libvirt,fabianfreyer/libvirt