[INTERNAL][FIX] sap.m.Select: fix arrow alignment in windows phone 8.1

The dropdown arrow is not centered vertically in windows phone 8.1 when selecting.

Change-Id: Ia9a2b3595b13359a2bc47efd462d6bba8116af45
Merge "[INTERNAL][FIX] sap.m.Select: fix arrow alignment in windows phone 8.1"