LU-16872 lod: reset llc_ostlist when using O_APPEND stripes

LU-16872 lod: reset llc_ostlist when using O_APPEND stripes

Files created with O_APPEND can have special striping set with the
parameters mdd.*.append_stripe_count and mdd.*.append_pool, and
should not inherit a list of OSTs to use from a parent directory
when these parameters are set. However, if a file is created with
O_APPEND and its create is handled by a kernel thread that has
previously created a file with a default list of OSTs, then those
defaults were erroneously applied to the O_APPEND file. This can
lead to the create returning EINVAL or to a crash.

This commit ensures that llc_ostlist is cleared when a file is
created with special append stripes.

Signed-off-by: Thomas Bertschinger <bertschinger@lanl.gov>
Change-Id: Ib2023e17c9ef31a2e029e09e67b257eb2c77b113
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/51559
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Lai Siyao <lai.siyao@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>