tree-wide: no need to pass excess flags to open()/openat() if O_PATH is passed

tree-wide: no need to pass excess flags to open()/openat() if O_PATH is passed

As described in the documentation:

When O_PATH is specified in flags, flag bits other than O_CLOEXEC,
O_DIRECTORY, and O_NOFOLLOW are ignored.

So, we can remove unnecessary flags in a case when O_PATH is passed
to the open() or openat().