ssa.c: Remove a couple of no longer used defines

SMDB_PRELOAD_PATH and PRDB_PRELOAD_PATH are now unused.

This is since the following commits:

commit d982edf86dd5691268a3881dff856d99349b8a58
Author: Hal Rosenstock <hal@mellanox.com>
Date:   Fri Oct 31 17:53:11 2014 +0200

    distrib: Eliminated no longer used or needed INETGRATION and ACCESS_INTEGRAT

    Signed-off-by: Hal Rosenstock <hal@mellanox.com>

commit 3587f045f30b5a69d92921f2458b120445ff4131
Author: Hal Rosenstock <hal@mellanox.com>
Date:   Fri Oct 31 17:39:07 2014 +0200

    core: Eliminated no longer used or needed CORE_INTEGRATION define

    Signed-off-by: Hal Rosenstock <hal@mellanox.com>

Signed-off-by: Sasha Kotchubievsky <sashakot@mellanox.com>
Signed-off-by: Hal Rosenstock <hal@mellanox.com>
ssa.c: Limit scope of thpool_rclose variable to the ssa.c file

Signed-off-by: Sasha Kotchubievsky <sashakot@mellanox.com>
Signed-off-by: Hal Rosenstock <hal@mellanox.com>
ssa.c: Release GError object where appropriate

From https://developer.gnome.org/gconf/stable/gconf-gconf-error.html
If an error occurs, a GError will be allocated and placed
in the return location; the caller must free the GError
with g_error_free().

Signed-off-by: Sasha Kotchubievsky <sashakot@mellanox.com>
Signed-off-by: Hal Rosenstock <hal@mellanox.com>
ssa.c: Obtain number of available cores on the computer

 get_npproc function is used
 Number of cores is printed to log
ssa.c: Implement multithreaded PR computation.

 1. Current implementation is based on Glib's thread pool.
 2. Each PRDB calculation is a separate task
 3. Multithreaded calculation is used only during SMDB update
 4. Number of AL workers is number of available cores - 3.
    (upstream, downstream, access). It doesn't mean that
    that there is no context switch during PR computation.
    Also, probably, upstream, downstream, access are waiting
    for IO and doesn't spend actually CPU. The formula could
    be changed in future.
ssa.c: Store number of al workers in access context
ssa.c: Push a access task to thread pool only if number of workers > 1.

 Else, use access thread for the computation.
ssa.c: Print an error in case of g_thread_pool_push failure