[Tizen] Fix bug on intalling widget failed

It is caused by temp value in local function used by outer function.

BUG=https://crosswalk-project.org/jira/browse/XWALK-2403
[Tizen] Fix bug on checking item of reference

It is caused by wrongly computing length of widget base path.
Merge pull request #2371 from xuzhang/widgetsignature

[Tizen] Fix bug on intalling widget failed