add tcptype to prflx tcp candidates

Adds the missing tcptype to prflx tcp candidates as tcptype is mandatory per
RFC 6544 and if missing the candidate will contain double whitespace like this
  ... tcptype  generation ...
and will get rejected by the internal parser

BUG=webrtc:11423

Change-Id: Id61babd85cf43d56e9e6f9bf30d4cc9e00f00f60
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/170442
Reviewed-by: Taylor <deadbeef@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30959}

p2p/base/tcp_port.cc

diff --git a/p2p/base/tcp_port.cc b/p2p/base/tcp_port.cc
index e07361a..efbf62e 100644
--- a/p2p/base/tcp_port.cc
+++ b/p2p/base/tcp_port.cc
@@ -122,7 +122,8 @@
     return NULL;
   }
 
-  if (address.tcptype() == TCPTYPE_ACTIVE_STR ||
+  if ((address.tcptype() == TCPTYPE_ACTIVE_STR &&
+       address.type() != PRFLX_PORT_TYPE) ||
       (address.tcptype().empty() && address.address().port() == 0)) {
     // It's active only candidate, we should not try to create connections
     // for these candidates.