Btrfs: remove root_log_ctx from ctx list before btrfs_sync_log returns

Btrfs: remove root_log_ctx from ctx list before btrfs_sync_log returns

We use a btrfs_log_ctx structure to pass information into the
tree log commit, and get error values out.  It gets added to a per
log-transaction list which we walk when things go bad.

Commit c19c47607 added an optimization to skip waiting for the log
commit, but didn't take root_log_ctx out of the list.  This
patch makes sure we remove things before exiting.

Signed-off-by: Chris Mason <clm@fb.com>
Fixes: c19c4760727f0d54266308cb81ff9ec3b38b5476
cc: stable@vger.kernel.org # 3.15+