chgserver: add merge-tools to sensitive config items

Because this can change whether the ui is gui or not.

This fixes test-extdiff.t with chg.

mercurial/chgserver.py

@@ -80,10 +80,12 b' def _hashlist(items):'
 # sensitive config sections affecting confighash
 _configsections = [
     b'alias',  # affects global state commands.table
+    b'diff-tools',  # affects whether gui or not in extdiff's uisetup
     b'eol',  # uses setconfig('eol', ...)
     b'extdiff',  # uisetup will register new commands
     b'extensions',
     b'fastannotate',  # affects annotate command and adds fastannonate cmd
+    b'merge-tools',  # affects whether gui or not in extdiff's uisetup
     b'schemes',  # extsetup will update global hg.schemes
 ]