cppcheck: resolve double free

The double free reported for the realloc() failure branch is a
false positive. It should be resolved in cppcheck 2.4 but for
the benefit of older versions we supress the warning.

https://trac.cppcheck.net/ticket/9292

Reviewed-by: Ryan Moeller <ryan@ixsystems.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #11508