Fixed critical Sonar issue. SimpleDateFormat was declared as a static
but it is not tread-safe and it keeps an internal state.
Compliant solution has been applied with additional DateUtil class.
Issue-ID: PORTAL-590 Signed-off-by: Robert Bogacki <r.bogacki@samsung.com>
Change-Id: Ic6243052804a410cb750c6c219c702469c86ff78