Fix use-after-free bugs in icp code

These were reported by Coverity as "Read from pointer after free" bugs.
Presumably, it did not report it as a use-after-free bug because it does
not understand the inline assembly that implements the atomic
instruction.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Closes #13881