s3:vfs:gpfs: fix flapping offline: always get winAttrs from gpfs for is_offline

s3:vfs:gpfs: fix flapping offline: always get winAttrs from gpfs for is_offline

There is a problem of flapping offline due to uninitialized
stat buffers. Due to a optimization in vfswrap_readdir which
directly calling fastatat (i.e. not through vfs), marking the
stat buffer valid, there is nothing this module can do about
it and hence can not currently not rely on the vaildity of
the stat buffer.

By always calling out to GPFS even when the stat buffer is
flagged valid, we can always return correct offline information,
thereby sacrificing the readdir optimization.

Pair-Programmed-With: Volker Lendecke <vl@samba.org>

Signed-off-by: Michael Adam <obnox@samba.org>
Reviewed-by: Christof Schmitt <cs@samba.org>
(cherry picked from commit 31e67507144aae8d5a8ec49587ac89d2d94636f0)

BUG: https://bugzilla.samba.org/show_bug.cgi?id=10741