fusefs: ignore FUSE_NO_OPEN(DIR)_SUPPORT flags

The FUSE_NO_OPEN_SUPPORT and FUSE_NO_OPENDIR_SUPPORT flags
are only meant to indicate kernel features, and should be ignored
if they appear in the FUSE_INIT reply flags.

Also fix the corresponding test cases.

MFC after: 2 weeks
Reviewed by: Alan Somers <asomers@FreeBSD.org>
Signed-off-by: CismonX <admin@cismon.net>
Pull Request: https://github.com/freebsd/freebsd-src/pull/1509