rtos: Add Inactive return to thread get state

If a thread hasn't been started return Inactive as the status when
Thread::get_state() is called.

Author: c1728p9

rtos/Thread.cpp

@@ -179,11 +179,15 @@ int32_t Thread::signal_clr(int32_t signals) {
 Thread::State Thread::get_state() {
 #if !defined(__MBED_CMSIS_RTOS_CA9) && !defined(__MBED_CMSIS_RTOS_CM)
 #ifdef CMSIS_OS_RTX
-    State status = Deleted;
+    State status;
     _mutex.lock();
 
     if (_tid != NULL) {
         status = (State)_thread_def.tcb.state;
+    } else if (_finished) {
+        status = Deleted;
+    } else {
+        status = Inactive;
     }
 
     _mutex.unlock();

rtos/Thread.h

@@ -252,7 +252,7 @@ class Thread {
 
     /** State of the Thread */
     enum State {
-        Inactive,           /**< Not created or terminated */
+        Inactive,           /**< Not created */
         Ready,              /**< Ready to run */
         Running,            /**< Running */
         WaitingDelay,       /**< Waiting for a delay to occur */