Delete temp files

Delete temp files

[Problem] Storage directory's size becomes huge (over 6MB)
 after infinite rebooting test.
[Cause & Measure] Over 1,500 temp files were created as followings.
 g_file_contents_set() creates temp file and writes contents to it. After that,
 rename temp file to destination file for atomic operation. If a device turned
 off before renaming, temp file remains and never be deleted.
 This patch deletes temp files before creating temp files.

4.0K    /opt/var/lib/bluetooth/FC:A6:21:B2:E1:7B/settings.CKX5BZ
4.0K    /opt/var/lib/bluetooth/FC:A6:21:B2:E1:7B/settings.OA76BZ
4.0K    /opt/var/lib/bluetooth/FC:A6:21:B2:E1:7B/settings.1BFTBZ
4.0K    /opt/var/lib/bluetooth/FC:A6:21:B2:E1:7B/settings.3CB9BZ

[Checking Method] Reboot device while booting

Change-Id: Ie159ef06eab6295b1f40514e4dde386a512eb5d1