Prevent sending broadcasts for non-changing properties.

This CL prevent sending broadcast for bluetooth device in case property
actually was not changed. This behaviour may depend on bluetooth layer
implementation details however it is good to have such guard here.

Original CL: ag/2955737

Bug: 66917724
Test: Build ok
Change-Id: Iaf553412ed0bf00fba4ac23bfcb82231379694cb