LU-6081 user: use random() instead of /dev/urandom

LU-6081 user: use random() instead of /dev/urandom

/dev/urandom gives good random numbers, but using it is very prone to
error, and opening/closing the device every time a number is needed
takes time.

Instead, initializes the library with our seed by calling srandom(),
and then use random(). Export a boolean variable
liblustreapi_initialized to let applications check that the library
was properly initialized by the loader.

Signed-off-by: frank zago <fzago@cray.com>
Signed-off-by: Henri Doreau <henri.doreau@cea.fr>
Change-Id: Ie6ced0d39df29d7054919e239add58a23115ec35
Reviewed-on: http://review.whamcloud.com/13277
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>