Fix NFC onManualBeamInvoke issue with policy

Clear NFC data in onManualBeamInvoke, to avoid previously cached NFC
data from being used despite beam is disallowed by policy

Note: There is still a potential problem when onManualBeamInvoke is
invoked in app's onResume. If you start the work app, disallow in
policy, then call onManualBeamInvoke in onResume, beam will still be
triggered and send out data. However, this is kind of an edge case as
app won't normally call onManualBeamInvoke in onResume, and only happens
if policy changed while the app has launched.

Bug: 21742271
Change-Id: Ib1bf340fd727962590b21945b253c980f079c0b8