fix test-bisect error (because of set -e)

tests/test-bisect

@@ -71,4 +71,4 b' hg bisect -s'
 
 echo % test no action
 hg bisect -r
-hg bisect
+hg bisect || echo failure

tests/test-bisect.out

@@ -285,3 +285,4 b' summary: msg 2'
 
 % test no action
 abort: cannot bisect (no known good revisions)
+failure