subrepo: make "_sanitize()" work "_sanitize()" was introduced by 224e96078708 on "stable" branch, but it has done nothing for sanitizing since 224e96078708. "_sanitize()" assumes "Visitor" design pattern: "os.walk()" should invoke specified function ("v" in this case) for each directory elements under specified path but "os.walk()" assumes "Iterator" design pattern: callers of it should drive loop to scan each directory elements under specified path by themselves with the returned generator object Because of this mismatching, "_sanitize()" just discards the generator object returned by "os.walk()" and does nothing for sanitizing. This patch makes "_sanitize()" work. This patch also changes the format of warning message to show each unlinked files, for multiple appearances of "potentially hostile .hg/hgrc".