[scm] Add lock around all set calls

Bug: b/356935829
Change-Id: I886d20b71af26efd828d18cb1b01f1271f42d053
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/5786165
Commit-Queue: Allen Li <ayatane@chromium.org>
Reviewed-by: Josip Sokcevic <sokcevic@chromium.org>

scm.py

@@ -404,6 +404,7 @@ class GitConfigStateReal(GitConfigStateBase):
         args = ['config', f'--{scope}', '--replace-all', key, value]
         if value_pattern is not None:
             args.append(value_pattern)
+        with self._scope_lock(scope):
             GIT.Capture(args, cwd=self.root)
 
     def unset_config(self, key: str, *, scope: GitConfigScope,
@@ -411,6 +412,7 @@ class GitConfigStateReal(GitConfigStateBase):
         # NOTE: `git config` already canonicalizes key.
         accepted_retcodes = (0, 5) if missing_ok else (0, )
         try:
+            with self._scope_lock(scope):
                 GIT.Capture(['config', f'--{scope}', '--unset', key],
                             cwd=self.root,
                             accepted_retcodes=accepted_retcodes)
@@ -429,6 +431,7 @@ class GitConfigStateReal(GitConfigStateBase):
         if value_pattern is not None:
             args.append(value_pattern)
         try:
+            with self._scope_lock(scope):
                 GIT.Capture(args,
                             cwd=self.root,
                             accepted_retcodes=accepted_retcodes)