samba: Swap libnss_win*.so* files and symlinks

The libnss_wins and libnss_winbind libraries were installed in this way:
/lib/libnss_<service>.so
/lib/libnss_<service>.so.<major> -> /lib/libnss_<service>.so

This had been done like this in order to get something similar to the
other NSS libraries, which are usually installed in this way:
/lib/libnss_<service>-<version>.so
/lib/libnss_<service>.so.<major> -> /lib/libnss_<service>-<version>.so

However, besides these files, these other NSS libraries usually come
installed with:
/usr/lib/libnss_<service>.so -> /lib/libnss_<service>.so.<major>

This means that the NSS libraries follow the usual library installation
practice, i.e. that the non-versioned .so is a symlink to the versioned
.so, so that switching versions is easy. In the case of the NSS
libraries, the versioned .so is just also a symlink to a .so with a more
accurate version.

Hence, follow the same rules for libnss_win*.so*, and install these
libraries the other way around:
/lib/libnss_<service>.so -> /lib/libnss_<service>.so.<major>
/lib/libnss_<service>.so.<major>

This is also how these libraries are installed by a major OS like Ubuntu
14.10:
/lib/x86_64-linux-gnu/libnss_winbind.so -> libnss_winbind.so.2
/lib/x86_64-linux-gnu/libnss_winbind.so.2
/lib/x86_64-linux-gnu/libnss_wins.so -> libnss_wins.so.2
/lib/x86_64-linux-gnu/libnss_wins.so.2

Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau.dev@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>