Bug#702782: broken glx alternative

[Andreas Beckmann]

new non-interactive commands to reproduce and fix:

# apt-get install --no-install-recommends xserver-xorg-video-nvidia
# apt-get install --no-install-recommends xserver-xorg-video-nvidia-legacy-173xx
# update-alternatives --set nvidia /usr/lib/nvidia/legacy-173xx
# ldd /usr/lib/xorg/modules/linux/libglx.so
        linux-vdso.so.1 =>  (0x00007fffda5ff000)
        libGLcore.so.1 => not found
        libnvidia-tls.so.1 => not found
        libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f76da242000)
        /lib64/ld-linux-x86-64.so.2 (0x00007f76dabe0000)
# dpkg-reconfigure glx-alternative-nvidia
update-alternatives: warning: forcing reinstallation of alternative /usr/lib/nvidia because link group glx is broken
# ldd /usr/lib/xorg/modules/linux/libglx.so
        linux-vdso.so.1 =>  (0x00007fffa873f000)
        libGLcore.so.1 => /usr/lib/x86_64-linux-gnu/libGLcore.so.1 (0x00007f3d12dd8000)
        libnvidia-tls.so.1 => /usr/lib/x86_64-linux-gnu/tls/libnvidia-tls.so.1 (0x00007f3d12cd7000)
        libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f3d1294c000)
        /lib64/ld-linux-x86-64.so.2 (0x00007f3d1445d000)

Andreas