s3: Fix streams enumeration bug in OneFS implementation

s3: Fix streams enumeration bug in OneFS implementation

Previously, we didn’t call SMB_VFS_OPEN_DIR from the streams module,
instead we called fdopendir(). As a result we failed to populate the
dir_state list in the readdirplus module. So when we tried to view the
stream data, we will always returned NULL.

To solve this I separated onefs_opendir() and the initialization of
the dir_state list. This is done by introducing a new utility function
“onefs_rdp_add_dir_state()”, which initializes the dir_state structure
and adds it to the dir_state list.  This function is called from the
streams module before calling readdir().