BUG/MINOR: tcp_sample: bc_{dst,src} return IP not INT

BUG/MINOR: tcp_sample: bc_{dst,src} return IP not INT

bc_{dst,src} sample fetches were introduced in 7d081f0 ("MINOR:
tcp_samples: Add samples to get src/dst info of the backend connection")

However a copy-pasting error was probably made here because they both
return IP addresses (not integers) like their fc_{src,dst} or src,dst
analogs.

Hopefully, this had no functional impact because integer can be converted
to both IPV4 and IPV6 types so the compatibility checks were not affected.

Better fix this to prevent confusion in code and "haproxy -dKsmp" output.

This should be backported up to 2.4 with 7d081f0.