Miscellaneous changes for RHEL 7.
    
    - Use 'make check -k' so we get to see all test failures at once.
    - For RHEL 7:
      * Do not depend on perl(Expect) (only needed to test virt-rescue).
      * Depend on /usr/bin/qemu-img instead of qemu-img package, since the
        package name (but not the binary) is different in RHEL 7.
      * Add workaround for libvirt/KVM bug RHBZ#878406.
      * Do not depend on libvirt-daemon-qemu.