Fixed typo in readFile from Utils.cpp

:Release Notes:
Make luna-sysservice able to start.

:Detailed Notes:
Utils.cpp:
- fix typo in readFile
- fix warning in createTempFile

:Testing Performed:
Without this change LunaSysService refuses to start on desktop build
with errors like:
PrefsDb::synchronizeDefaults(): Failed to load default prefs file: /mnt/devel/build/build-luna-surface-manager-desktop/build/staging/etc/palm/defaultPreferences.txt

:QA Notes:

:Issues Addressed:

Open-webOS-DCO-1.0-Signed-off-by: Nikolay Orliuk <nikolay.orliuk@lge.com>
Change-Id: I1490274ddb78c4d6f84abd3a477b810674a8ce63
Reviewed-on: https://g2g.palm.com/3936
Reviewed-by: DCO Verification
Reviewed-by: Nikolay Orliuk <nikolay.orliuk@lge.com>
Tested-by: Nikolay Orliuk <nikolay.orliuk@lge.com>
Reviewed-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>