mptcp: add_addr: new retry test without errors

On very slow hosts, injected packets cause troubles because it reset
timers in Packetdrill, see:

  multipath-tcp/mptcp_net-next#312

Add a new "safer" version without these injected packets to monitor if
everything is OK like that.

Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
(cherry picked from commit 59cd5dd)
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>

gtests/net/mptcp/add_addr/add_addr_retry_plain.pkt

@@ -0,0 +1,34 @@
+// connection initiated by packetdrill
+--tolerance_usecs=200000
+`../common/defaults.sh`
+
++0     `sysctl -wq net.mptcp.add_addr_timeout=1`
++0     `../common/multi-ep.sh -e 1 -m signal`
+
++0     socket(..., SOCK_STREAM, IPPROTO_MPTCP) = 3
++0     setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
+
++0     bind(3, ..., ...) = 0
++0     listen(3, 1) = 0
++0       <  S   0:0(0)               win 32792  <mss 1460, sackOK, nop, nop, nop, wscale 7, mpcapable v1 flags[flag_h] nokey>
++0       >  S.  0:0(0)        ack 1             <mss 1460, nop, nop, sackOK, nop, wscale 8, mpcapable v1 flags[flag_h] key[skey]>
++0.01    <   .  1:1(0)        ack 1  win 257                                               <mpcapable v1 flags[flag_h] key[ckey=2, skey]>
++0     accept(3, ..., ...) = 4
+
+// ADD_ADDR is sent directly (>= 5.12), not after first data (< 5.12)
++0       >   .  1:1(0)        ack 1           <add_address address_id=1  addr[saddr0] hmac=auto>
+
+// Retransmitted after one second
++1.0     >   .  1:1(0)        ack 1           <add_address address_id=1  addr[saddr0] hmac=auto>
++1.0     >   .  1:1(0)        ack 1           <add_address address_id=1  addr[saddr0] hmac=auto>
+
+// send echo with correct id, expect no retry
++0       <   .  1:1(0)        ack 1  win 257  <add_address address_id=1  addr[saddr0] addr_echo>
+
+// read and ack 1 data segment
++1.1     <  P.  1:1001(1000)  ack 1  win 450  <nop, nop, dss dack8=1    dsn8=1 ssn=1 dll=1000 nocs>
++0       >   .  1:1(0)        ack 1001                  <dss dack8=1001        ssn=1 dll=0 nocs>
++0.3   read(4, ..., 1000) = 1000
+
++0     close(4) = 0
++0       >   .  1:1(0)        ack 1001                  <dss dack8=1001 dsn8=1 ssn=0 dll=1 nocs fin, nop, nop>