m_clrprotoflags() is designed to cleanup M_PROTO flags when mbufs cross
protocol and facility boundaries.  However, now it cleans up only the
first mbuf, while intent clearly means all mbufs in a possible chain.

Differential Revision:	https://reviews.freebsd.org/D1352
Reviewed by:		rpaulo, gnn, adrian
Sponsored by:		Nginx, Inc.


git-svn-id: svn+ssh://svn.freebsd.org/base/head@276136 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f