There are various cases where we modify the inp_vflag and inp_inc.inc_flags

There are various cases where we modify the inp_vflag and inp_inc.inc_flags
fields during a syscall, but don't restore those fields if the operation
fails.  This can leave the inp structure in an inconsistent state and cause
various problems.

Restore the inp_vflag and inp_inc.inc_flags fields when the underlying
operation fails and the inp could be in an inconsistent state.

This is a direct commit to the branch as the code is different enough in
the other branches to make it difficult to resolve a merge.

Submitted by:	jtl@
Reported by:	Jakub Jirasek, Secunia Research at Flexera
Reviewed by:	jhb@
Approved by:	so
Security:	FreeBSD-EN-18:11.listen
Security:	CVE-2018-6925

git-svn-id: svn://svn.freebsd.org/base/stable/10@338985 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f