ssh: test some no-op pull through ssh with --debug

It appears that we are never running any wireprotocol operation with a --debug
flag. So we are adding some basic testing into 'test-ssh.t'

tests/test-ssh.t

@@ -445,6 +445,29 stderr from remote commands should be pr
   remote: KABOOM
   local stdout
 
+debug output
+
+  $ hg pull --debug ssh://user@dummy/remote
+  pulling from ssh://user@dummy/remote
+  running python "*/dummyssh" user@dummy 'hg -R remote serve --stdio' (glob)
+  sending hello command
+  sending between command
+  remote: 271
+  remote: capabilities: lookup changegroupsubset branchmap pushkey known getbundle unbundlehash batch stream bundle2=HG20%0Achangegroup%3D01%2C02%0Adigests%3Dmd5%2Csha1%2Csha512%0Alistkeys%0Apushkey%0Aremote-changegroup%3Dhttp%2Chttps unbundle=HG10GZ,HG10BZ,HG10UN httpheader=1024
+  remote: 1
+  preparing listkeys for "bookmarks"
+  sending listkeys command
+  preparing listkeys for "bookmarks"
+  sending listkeys command
+  query 1; heads
+  sending batch command
+  searching for changes
+  all remote heads known locally
+  no changes found
+  preparing listkeys for "phases"
+  sending listkeys command
+  checking for updated bookmarks
+
   $ cd ..
 
   $ cat dummylog
@@ -478,3 +501,4 stderr from remote commands should be pr
   Got arguments 1:user@dummy 2:hg -R 'a repo' serve --stdio
   Got arguments 1:user@dummy 2:hg -R remote serve --stdio
   changegroup-in-remote hook: HG_NODE=65c38f4125f9602c8db4af56530cc221d93b8ef8 HG_SOURCE=serve HG_TXNID=TXN:* HG_URL=remote:ssh:127.0.0.1 (glob)
+  Got arguments 1:user@dummy 2:hg -R remote serve --stdio