REGTESTS: checks: exclude freebsd target for tcp-check_multiple_ports.vtc

REGTESTS: checks: exclude freebsd target for tcp-check_multiple_ports.vtc

This patch excludes freebsd, osx and generic targets for this vtc.

Basic tcp checks performed by haproxy on a linux system leverage the
TCP_QUICKACK option which implies that the connection is never
established from the perspective of the backend server. On other systems
a regular tcp 3 way handshake is performed immediately followed by a
reset, which from the perspective of the server is an aborted connection.

When we run this regtest on FreeBSD (or anything other than linux) there
is a race condition in the server_thread() function of the vtc_server.c
file. If we receive the reset when we are in accept() then fd is -1 and
vtest calls vtc_fatal, failing the test.

Other checks specific reg-tests were excluded on FreeBSD, osx and
generic for the same reason, but were at the time documented as being
disabled because they used TCP_DEFER_ACCEPT. These commits are
15685c791 ("REGTEST: Exclude freebsd target for some reg tests") and
03c6ab0cb ("REGTEST: exclude osx and generic targets for
40be_2srv_odd_health_checks")