Remove some cppcheck style warnings

lib/driver/gnu_linux.c

@@ -660,10 +660,8 @@ static int do_umount(char * target) {
     execlp("pumount", "pumount", target, NULL);
     execlp("umount", "umount", target, NULL);
     return -1;
-    break;
   case -1:
     return -1;
-    break;
   default: /* parent */
     wait(&status);
     if (WIFEXITED(status) == 0) {

lib/driver/image/bincue.c

@@ -257,7 +257,7 @@ parse_cuefile (_img_private_t *cd, const char *psz_cue_name)
 
   /* The below declarations may be unique to this image-parse routine. */
   int start_index;
-  bool b_first_index_for_track=false;
+  bool b_first_index_for_track;
 
   if (NULL == psz_cue_name) 
     return false;

lib/driver/image/nrg.c

@@ -507,7 +507,6 @@ parse_nrg (_img_private_t *p_env, const char *psz_nrg_name,
 		    opcode==NERO_ID ? 'O': '5');
 	free(footer_buf);
 	return false;
-	break;
 
       case END1_ID: /* "END!" */
 	cdio_debug ("nrg end tag detected");