Fix "This Seq has already been iterated" when tapping a feed

@DaTa <== map {$_ + 1} <== @tap <== grep {$_ % 2} <== eager @DaTa;
pushed the Seq from grep into @tap and then tried to re-use the same Seq
for further processing of the feed in map. Have to .list it to do that.

Fixes t/spec/S03-feeds/basic.t

src/Perl6/Actions.nqp

@@ -5576,7 +5576,10 @@ Compilation unit '$file' contained the following violations:
                     QAST::Op.new(
                         :op('bind'),
                         QAST::Var.new( :scope('local'), :name($tmp), :decl('var') ),
-                        QAST::Op.new( :op('call'), $result )
+                        QAST::Op.new(
+                            :op('callmethod'), :name('list'),
+                            QAST::Op.new( :op('call'), $result )
+                        ),
                     ),
                     QAST::Op.new(
                         :op('callmethod'), :name('push'),