safehasattr: pass attribute name as string instead of bytes

This is a step toward replacing `util.safehasattr` usage with plain `hasattr`.
The builtin function behave poorly in Python2 but this was fixed in Python3.

These change are done one by one as they tend to have a small odd to trigger
puzzling breackage.

mercurial/chgserver.py

@@ -603,7 +603,7 b' class chgcmdserver(commandserver.server)'
         }
     )
 
-    if util.safehasattr(procutil, b'setprocname'):
+    if util.safehasattr(procutil, 'setprocname'):
 
         def setprocname(self):
             """Change process title"""