[dolphin/search] Avoid unnecesary reloads on setSearchPath

[dolphin/search] Avoid unnecesary reloads on setSearchPath

Summary:
Check in `setSearchPath()` if the `url` passed is already the `searchPath`
This was causing an effect where reloading the same search URL results on buttons `From Here/Everywhere` toggling.
See D24422

Test Plan:
On your home folder press `Ctrl-F` several times
Buttons `From Here/Everywhere` should now not toggle each time

Reviewers: #dolphin, elvisangelaccio, meven, ngraham

Reviewed By: #dolphin, ngraham

Subscribers: kfm-devel

Tags: #dolphin

Differential Revision: https://phabricator.kde.org/D24449