fix(upgrade): ensure files in BINDIR executable

During upgrade procedure, emqx zip file is repacked to .tar.gz but does not
preserve permission of files.

This commit ensure files under BINDIR is executable

bin/emqx

@@ -42,6 +42,8 @@ assert_node_alive() {
 }
 
 check_erlang_start() {
+    # Fix bin permission
+    find "$BINDIR" ! -executable -exec chmod a+x {} \;
     "$BINDIR/$PROGNAME" -boot "$REL_DIR/start_clean" -eval "crypto:start(),halt()"
 }