8603 rename zilog's "zl_writer_lock" to "zl_issuer_lock"
illumos/illumos-gate@cf07d3da9915c0d22da8f59e991639f819463cef
https://www.illumos.org/issues/8603:
To help make the ZIL's code more understandable, it was suggested that the zilog_t's "zl_writer_lock" field should be renamed to "zl_issuer_lock".