Fix nasa#1024, check misc API return codes

Fix missing doxygen retvals

Note, other tests were OK, but depend on support being enabled and
supported by RTOS.  Script will report N/A items (due to no impl) as
missing.  Confirmed OS_HeapGetInfo OK on RTEMS.

src/os/inc/osapi-heap.h

@@ -53,6 +53,7 @@ typedef struct
  * @param[out] heap_prop Storage buffer for heap info
  *
  * @return Execution status, see @ref OSReturnCodes
+ * @retval #OS_SUCCESS @copybrief OS_SUCCESS
  * @retval #OS_INVALID_POINTER if the heap_prop argument is NULL
  */
 int32 OS_HeapGetInfo(OS_heap_prop_t *heap_prop);

src/os/inc/osapi-network.h

@@ -65,6 +65,7 @@ int32 OS_NetworkGetID(void);
  * @param[in]   name_len     Maximum length of host name buffer
  *
  * @return Execution status, see @ref OSReturnCodes
+ * @retval #OS_SUCCESS @copybrief OS_SUCCESS
  * @retval #OS_ERR_INVALID_SIZE if the name_len is zero
  * @retval #OS_INVALID_POINTER if the host_name is NULL
  */

src/unit-tests/oscore-test/ut_oscore_misc_test.c

@@ -418,23 +418,15 @@ void UT_os_heapgetinfo_test(void)
 {
     OS_heap_prop_t heapProp;
 
-    /*-----------------------------------------------------*/
-    /* API not implemented */
-
-    if (!UT_IMPL(OS_HeapGetInfo(&heapProp)))
-    {
-        return;
-    }
-
     /*-----------------------------------------------------*/
     /* #1 Null-pointer-arg */
 
     UT_RETVAL(OS_HeapGetInfo(NULL), OS_INVALID_POINTER);
 
     /*-----------------------------------------------------*/
-    /* #3 Nominal */
+    /* #3 Nominal (allows for not implemented) */
 
-    UT_NOMINAL(OS_HeapGetInfo(&heapProp));
+    UT_NOMINAL_OR_NOTIMPL(OS_HeapGetInfo(&heapProp));
 }
 
 /*================================================================================*

src/unit-tests/osfile-test/ut_osfile_fileio_test.c

@@ -1421,6 +1421,14 @@ void UT_os_outputtofile_test()
                 UtAssert_True(strstr(g_readBuff, "UT_os_outputtofile_test") != NULL,
                               "Output file contains UT_os_outputtofile_test");
             }
+
+            /*
+             * Executing a command name "false" should fail, either because it is not a known
+             * command, or if it is valid (e.g. a UNIX-like environment has /bin/false) the
+             * command always fails.
+             */
+            UT_RETVAL(OS_ShellOutputToFile("false", g_fDescs[0]), OS_ERROR);
+
         }
 
         /* Reset test environment */