test-glog: avoid check-code violation after next patch

Danek's patch will help us avoid spurious test breakages on
Solaris. This test wasn't broken on Solaris because of the grep(1)
use, but it will upset check-code. Use cmp to silence check-code since
it doesn't matter.

tests/test-glog.t

@@ -1429,7 +1429,8 b' Test log -G options'
   >     | sed 's/.*nodetag/nodetag/' > log.nodes
   >   hg log -G --template 'nodetag {rev}\n' "$@" | grep nodetag \
   >     | sed 's/.*nodetag/nodetag/' > glog.nodes
-  >   diff -u log.nodes glog.nodes | grep '^[-+@ ]' || :
+  >   (cmp log.nodes glog.nodes || diff -u log.nodes glog.nodes) \
+  >     | grep '^[-+@ ]' || :
   > }
 
 glog always reorders nodes which explains the difference with log