[FIX] sap.m.Link: fix error when set to non-subtle/non-emphasized
[FIX] sap.m.Link: fix error when set to non-subtle/non-emphasized

When default value was explicitly set again in the constructor, there
was a JS error. Also when It was set later repeatedly in
non-accessibility mode.
This bug was introduced on December 19th, in master only.

Change-Id: Ifad0d451d6f323ad09226cc082b28ac39a22f4c7
BCP: 1472023641


cschuff/openui5,nzamani/openui5,SQCLabs/openui5,SAP/openui5,SAP/openui5,nzamani/openui5,olirogers/openui5,olirogers/openui5,SAP/openui5,olirogers/openui5,cschuff/openui5,nzamani/openui5,SAP/openui5,SQCLabs/openui5,cschuff/openui5,SQCLabs/openui5