Fix two shadow compiler warnings

  CC	fd-files.o
fd-files.c: In function ‘list_to_index’:
fd-files.c:216:15: warning: declaration of ‘index’ shadows a global declaration [-Wshadow]
  CC	fds.o
fds.c: In function ‘process_disable_fds_param’:
fds.c:164:38: warning: declaration of ‘optarg’ shadows a global declaration [-Wshadow]

Signed-off-by: Brian Haley <brian.haley@hp.com>