Remove setting BIO_DONE flag for BIOs that have done() method.

This fixes use-after-free, caused by geom_disk, completing same BIO twice
to save extra allocation, and getting BIO_DONE set after the first.

MFC after:	1 week


git-svn-id: svn+ssh://svn.freebsd.org/base/head@273143 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f