Add calls to pthread_attr_destroy().

Add calls to pthread_attr_destroy().

This patch adds a couple of missing calls to pthread_attr_destroy().

There were a couple of instances where pthread_attr_init() was being
used without a cooresponding call to pthread_attr_destroy().  This also
localizes the pthread_attr_t to the function where it is needed instead
of having it persist (the man page specifically states that destroying
the attributes structure has no effect on threads created using the
attributes).

Signed-off-by: Russell Bryant <russell@russellbryant.net>
Reviewed-by: Steven Dake <sdake@redhat.com>