bdd: xfail broken yankpaste tests for now.

Using the clipboard seems to be a good recipe for a lot of weird pain.
Until we avoid it altogether (see #1285) we xfail those problematic tests.

tests/integration/features/yankpaste.feature

@@ -182,6 +182,8 @@ Feature: Yanking and pasting.
         And I run :paste -t
         Then no crash should happen
 
+    # https://github.com/The-Compiler/qutebrowser/issues/1285
+    @xfail
     Scenario: Pasting multiple urls with an almost empty one
         When I open about:blank
         And I put "http://localhost:(port)/data/hello.txt\n \nhttp://localhost:(port)/data/hello2.txt" into the clipboard
@@ -190,6 +192,8 @@ Feature: Yanking and pasting.
 
     #### :paste-primary
 
+    # https://github.com/The-Compiler/qutebrowser/issues/1285
+    @xfail
     Scenario: Pasting the primary selection into an empty text field
         When selection is supported
         And I open data/paste_primary.html