Fix intermittent crash on mutex test

The test tests-mbedmicro-rtos-mbed-mutex intermittently fails.
This patch fixes the problem by initializing thread attributes.
It also initializes attributes of other OS wrapper classes to prevent
them from having undefined behavior.

The test failure on tests-mbedmicro-rtos-mbed-mutex manifested as a
crash after running the test case "Test multiple thread" on the ARMCC
compiler. This is because one of the threads created for this test
happened to have uninitialized attribute bits set to joinable. This
caused a pointer to this task to be kept in the terminate_list even
after the thread had been deleted and gone out of scope. Later
when the RTX kernel accessed this deleted object a crash occurred.

Author: c1728p9

rtos/Mutex.cpp

@@ -29,6 +29,7 @@ namespace rtos {
 
 Mutex::Mutex() {
     memset(&_obj_mem, 0, sizeof(_obj_mem));
+    memset(&_attr, 0, sizeof(_attr));
     _attr.cb_mem = &_obj_mem;
     _attr.cb_size = sizeof(_obj_mem);
     _attr.attr_bits = osMutexRecursive;

rtos/Queue.h

@@ -46,6 +46,7 @@ class Queue {
     /** Create and initialize a message Queue. */
     Queue() {
         memset(&_obj_mem, 0, sizeof(_obj_mem));
+        memset(&_attr, 0, sizeof(_attr));
         _attr.mq_mem = _queue_mem;
         _attr.mq_size = sizeof(_queue_mem);
         _attr.cb_mem = &_obj_mem;

rtos/RtosTimer.cpp

@@ -31,6 +31,7 @@ namespace rtos {
 void RtosTimer::constructor(mbed::Callback<void()> func, os_timer_type type) {
     _function = func;
     memset(&_obj_mem, 0, sizeof(_obj_mem));
+    memset(&_attr, 0, sizeof(_attr));
     _attr.cb_mem = &_obj_mem;
     _attr.cb_size = sizeof(_obj_mem);
     _id = osTimerNew((void (*)(void *))Callback<void()>::thunk, type, &_function, &_attr);

rtos/Semaphore.cpp

@@ -28,6 +28,7 @@ namespace rtos {
 
 Semaphore::Semaphore(int32_t count, uint16_t max_count) {
     memset(&_obj_mem, 0, sizeof(_obj_mem));
+    memset(&_attr, 0, sizeof(_attr));
     _attr.cb_mem = &_obj_mem;
     _attr.cb_size = sizeof(_obj_mem);
     _id = osSemaphoreNew(max_count, count, &_attr);

rtos/Thread.cpp

@@ -39,6 +39,8 @@ void Thread::constructor(osPriority priority,
     _tid = 0;
     _dynamic_stack = (stack_mem == NULL);
     _finished = false;
+    memset(&_obj_mem, 0, sizeof(_obj_mem));
+    memset(&_attr, 0, sizeof(_attr));
     _attr.priority = priority;
     _attr.stack_size = stack_size;
     _attr.name = name;