[Tizen] Copy and paste cleanup in xwalk package installer

A similar call to InitializePkgmgrSignal and a quite long argument
preparation for the call was put in four different places.

Change-Id: Ib5adfd5b3dddfaed7c7c52b9f43745843b5df6cf
Merge pull request #2533 from tweglarski/CopyAndPasteCleanup

[Tizen] Copy and paste cleanup in xwalk package installer