Prevent gcc -Werror=maybe-uninitialized warnings in spa_wait_common()
This commit fixes the following build failure detected on Debian9
(GCC 6.3.0):
CC [M] module/zfs/spa.o
module/zfs/spa.c: In function ‘spa_wait_common.part.31’:
module/zfs/spa.c:9468:6: error: ‘in_progress’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
if (!in_progress || spa->spa_waiters_cancel || error)
^
cc1: all warnings being treated as errors
Reviewed-by: Chris Dunlop <chris@onthe.net.au> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: John Gallagher <john.gallagher@delphix.com> Signed-off-by: loli10K <ezomori.nozomu@gmail.com>
Closes #9326