util: fix human-readable printing of negative byte counts

Apply the same human-readable printing rules to negative byte counts as to
positive ones. Fixes output of debugupgraderepo.

mercurial/util.py

@@ -2161,7 +2161,7 b' def unitcountfn(*unittable):'
 
     def go(count):
         for multiplier, divisor, format in unittable:
-            if count >= divisor * multiplier:
+            if abs(count) >= divisor * multiplier:
                 return format % (count / float(divisor))
         return unittable[-1][2] % count