[FS#536] uci -m import duplicates list entries on repeated imports

[LEDE Bugs]

The following task has a new comment added:

FS#536 - uci -m import  duplicates list entries on repeated imports 
User who did this - yousong (yousong)

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I do not maintain uci, but looking at it again, I will still say no to this.

The arguments are almost the same

 1. UCI never tries to maintain uniqueness among values of list option.
 2. There are already other valid usages of having duplicate values in list values.
 3. Stripping out duplicate elements of list options can be done with some shell scripting.  It's very flexible
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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=536#comment1902