bgpd: dynamically allocate synchronization primitives

bgpd: dynamically allocate synchronization primitives

Changes all synchronization primitives to be dynamically allocated. This
should help catch any subtle errors in pthread lifecycles.

This change also pre-initializes synchronization primitives before
threads begin to run, eliminating a potential race condition that
probably would have caused a segfault on startup on a very fast box.

Also changes mutex and condition variable allocations to use
MTYPE_PTHREAD and updates tests to do the proper initializations.

Signed-off-by: Quentin Young <qlyoung@cumulusnetworks.com>