Revert "Fix data race between zil_commit() and zil_suspend()"

This reverts commit 4c856fb333ac57d9b4a6ddd44407fd022a702f00 to
resolve a newly introduced deadlock which in practice in more
disruptive that the issue this commit intended to address.

Reviewed-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Reviewed-by: Mark Maybee <mark.maybee@delphix.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #14775
Closes #14790