Disable sniff in link policy before a2dp streaming

Disable sniff mode unconditionally to the link policy
before a2dp streaming. This is to prevent a2dp link
going to sniff during streaming in case remote requests so.

Tag: #compatibility
Bug: 193206591
Test: Link policy settings for A2DP streaming
Change-Id: If98ba6ef7d2c1bf1777d780a9a80cd6b08f898f5