LU-5541 lustreapi: only export the API symbols

LU-5541 lustreapi: only export the API symbols

By default, all kind of symbols are exported from the library (dump,
libcfs_ukuc_start, l_ioctl, set_ioctl_dump, ...), which may create
external conflicts. Use the linker version-script options to only
export the API symbols, and prevent the export of internal symbols.

Only the symbols declared in the global section of liblustreapi.map
will be seen by applications.

Fix lshowmount to use libcfs and not internal liblustreapi symbol.

Change-Id: Ica4226c1ea9b6b159a056ad22bacaa2ffcf4b171
Signed-off-by: frank zago <fzago@cray.com>
Signed-off-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Reviewed-on: https://review.whamcloud.com/11643
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Henri Doreau <henri.doreau@cea.fr>