add testcase for sctp_add_streams

gtests/net/packetdrill/tests/bsd/sctp/sctp_reconfig/sctp_add_streams.pkt

+--tolerance_usecs=100000
+
+ 0.0 socket(..., SOCK_STREAM, IPPROTO_SCTP) = 3
++0.0 fcntl(3, F_GETFL) = 0x2 (flags O_RDWR)
++0.0 fcntl(3, F_SETFL, O_RDWR|O_NONBLOCK) = 0
++0.0 bind(3, ..., ...) = 0
+// Check the handshake with an empty(!) cookie
++0.1 connect(3, ..., ...) = -1 EINPROGRESS (Operation now in progress)
++0.0 > sctp: INIT[flgs=0, tag=1, a_rwnd=..., os=..., is=..., tsn=1, ...]
++0.1 < sctp: INIT_ACK[flgs=0, tag=2, a_rwnd=1500, os=16, is=16, tsn=1, STATE_COOKIE[len=4, val=...]]
++0.0 > sctp: COOKIE_ECHO[flgs=0, len=4, val=...]
++0.1 < sctp: COOKIE_ACK[flgs=0]
++0.0 getsockopt(3, SOL_SOCKET, SO_ERROR, [0], [4]) = 0
+
++0.0 setsockopt(3, IPPROTO_SCTP, SCTP_PEER_ADDR_PARAMS, {spp_assoc_id=3,
+                                                         spp_address={sa_family=AF_INET,
+                                                                      sin_port=htons(8080),
+                                                                      sin_addr=inet_addr("192.0.2.1")},
+                                                         spp_hbinterval=0,
+                                                         spp_pathmaxrxt=8,
+                                                         spp_pathmtu=1468,
+                                                         spp_flags=SPP_HB_DISABLE,
+                                                         spp_ipv6_flowlabel=0,
+                                                         spp_dscp=0}, 152) = 0
+
++0 setsockopt(3, IPPROTO_SCTP, SCTP_ENABLE_STREAM_RESET, {assoc_id=0, assoc_value=SCTP_ENABLE_RESET_STREAM_REQ}, 8) = 0
+
++0 setsockopt(3, IPPROTO_SCTP, SCTP_ADD_STREAMS, {sas_instrms=20,
+						  sas_outstrms=20}, 8) = 0
+
++0 close(3) = 0