Don't set FUSE_CAP_PARALLEL_DIROPS by default

Don't set FUSE_CAP_PARALLEL_DIROPS by default

Allowing parallel dir operations could result in a crash in a filesystem
implementation that is not prepared for this.

To be safe keep this flag off by default (this is not a regression, since
there was no public release where this flag wasn't ignored).

If the filesystem wants better performance, then it should set this flag
explicitly.

Fixes: c9905341ea34 ("Pass FUSE_PARALLEL_DIROPS to kernel (#861)")
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>