[FIX] sap.m.DateTimePicker: use of the dateValue property isn`t recommended
[FIX] sap.m.DateTimePicker: use of the dateValue property isn`t recommended

Attempts to access "dateValue" could lead to an unpredictable results. 
For the time being, the property "value" should be used instead.

BCP: N/A
JIRA: MI2C-3095

Change-Id: I0ec54b47ceb0bd551201ef32011b4f8fff83266b

SAP/openui5,SAP/openui5,SAP/openui5,SAP/openui5