Fix a long standing bug in the output buffer size computation.

git cherry-pick -e 2a7f2ae

liblog/fake_log_device.c

@@ -454,7 +454,7 @@ static void showLog(LogState *state,
 
     numVecs = numLines*3;  // 3 iovecs per line.
     if (numVecs > INLINE_VECS) {
-        vec = (struct iovec*)malloc(sizeof(struct iovec)*numLines);
+        vec = (struct iovec*)malloc(sizeof(struct iovec)*numVecs);
         if (vec == NULL) {
             msg = "LOG: write failed, no memory";
             numVecs = 3;