Add RPORT to the list of DCERPC ports to check

## Validation steps

- [ ] Start a DCERPC service on a port other than 135 or 593. WDS is delightful for this purpose, see #1420 for instructions from @Meatballs1
- [ ] Set the RPORT on auxiliary/scanner/dcerpc/endpoint_mapper to 5040 (assuming you go with WDS)
- [ ] Start wireshark or tcpdump with a BPF filter of "port 5040"

Without patch:

- [ ] See no traffic on port 5040.

With patch:

- [ ] See traffic on port 5040.