test-http: use sed instead of fixed-with cut for reading access.log

Some systems (like FreeBSD jails) use something other than 127.0.0.1
for localhost, and it's not safe to assume it'll always be the same
width. Using sed with a replacement like this sidesteps the problem.

tests/test-http-bundle1.t

@@ -234,7 +234,7 b' test http authentication'
   remote: added 1 changesets with 1 changes to 1 files
   $ hg rollback -q
 
-  $ cut -c38- ../access.log
+  $ sed 's/.*] "/"/' < ../access.log
   "GET /?cmd=capabilities HTTP/1.1" 200 -
   "GET /?cmd=lookup HTTP/1.1" 200 - x-hgarg-1:key=tip
   "GET /?cmd=listkeys HTTP/1.1" 401 - x-hgarg-1:namespace=namespaces

tests/test-http.t

@@ -225,7 +225,7 b' test http authentication'
   remote: added 1 changesets with 1 changes to 1 files
   $ hg rollback -q
 
-  $ cut -c38- ../access.log
+  $ sed 's/.*] "/"/' < ../access.log
   "GET /?cmd=capabilities HTTP/1.1" 200 -
   "GET /?cmd=lookup HTTP/1.1" 200 - x-hgarg-1:key=tip
   "GET /?cmd=listkeys HTTP/1.1" 401 - x-hgarg-1:namespace=namespaces