LU-1606 api: compile and build lustreapi test

To avoid regression of the client api conf-sanity includes a new test
73 to verify the lustreapi can be compiled and linked against. All the
files in the directory $LUSTRE_TESTS_API_DIR with the extension .c are
compiled and linked. The directory is located in the build tree at
./lustre/tests/clientapi.

Signed-off-by: Richard Henwood <richard.henwood@intel.com>
Change-Id: I0ad6a1671bf7033ec2ad5bc7a82d82e468cd31c2
Reviewed-on: http://review.whamcloud.com/3440
Tested-by: Hudson
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>