Issue title: CLI: prefix matching should be used when we match the  path.
 Issue body: https://github.com/apache/incubator-apisix/pull/1236/files#r392630774

```lua
if string.find(home_path, "/root/") == 1 then
    -- print warning message
end
```
 Comments: 
 Comment 0: @sshniro please take a look when you have time
 Comment 1: Solved.
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