packetdrill: run_all: pass netmask to remote_ip arg

[fw-strlen]

Makes no difference for upstream packetdrill, but this makes the
mptcp-fork 'join' tests work when run from the run_all script.

The mp_join tests add a secondary ip address. Without the netmask the kernel can't find a route for the syn/ack packet and the tcp syn carrying the join request never gets a response.

The netmasks are the ones used in the two DEFAULT_V{4,6}_LIVE_REMOTE_IP_STRING defines.

The basic-v{4,6} test cases are adjusted to add a host-specific route rather than attempt to change a
(now no longer existing) entry.

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[fw-strlen]

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