Modify tc and mm_heapinfo.c based on svace

Modify tc and mm_heapinfo.c based on svace

tc_libc_syslog.c : Use of vulnerable function 'sprintf' at tc_libc_syslog.c:90. This function is unsafe, use snprintf instead.
tc_libc_unistd.c : Use of vulnerable function 'sprintf' at tc_libc_unistd.c:279. This function is unsafe, use snprintf instead.
tc_pthread.c : No unlock for mutex 'g_mutex' at tc_pthread.c:1284 after lock at tc_pthread.c:1278 by calling function 'pthread_mutex_lock'.
tc_sched.c : Dynamic memory referenced by 'status' was allocated at tc_sched.c:306 by calling function 'malloc' and lost at tc_sched.c
mm_heapinfo.c : Return value of a function 'sched_gettcb' is dereferenced at mm_heapinfo.c:277 without checking, but it is usually checked for this function