maint: use EXIT_SUCCESS and EXIT_FAILURE, not 0 and 1 in "usage", too

maint: use EXIT_SUCCESS and EXIT_FAILURE, not 0 and 1 in "usage", too

Convert by running these commands:
perl -pi -e 's/\b(usage ?)\(1\)/$1(EXIT_FAILURE)/' \
  fish/fish.c fuse/guestmount.c
perl -pi -e 's/\b(usage ?)\(0\)/$1(EXIT_SUCCESS)/' \
  fish/fish.c fuse/guestmount.c
* fish/fish.c (main): Replace 0/1 with EXIT_SUCCESS/EXIT_FAILURE.
* fuse/guestmount.c (main): Likewise.