MFC: r285215

MFC: r285215

remove _NORMAL flag which isn't suppose to be used w/ _alloc_ctx...

MFC: r285289

address an issue where consumers, like IPsec, can reuse the same
session in multiple threads w/o locking..  There was a single fpu
context shared per session, if multiple threads were using the session,
and both migrated away, they could corrupt each other's fpu context...

MFC: r285297

upon further examination, it turns out that _unregister_all already
provides the guarantee that no threads will be in the _newsession code..

MFC: r298332

aesni(4): Initialize error before use [1]

Reported by:	Coverity [1]
CID:		1331554 [1]

git-svn-id: svn://svn.freebsd.org/base/stable/10@323871 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f