fix valgrind issues with recently added test in modules/blockonbackground (#9192)
fix valgrind issues with recently added test in modules/blockonbackground (#9192)

fixes test issue introduced in #9167

1. invalid reads due to accessing non-retained string (passed as unblock context).
2. leaking module blocked client context, see #6922 for info.

(cherry picked from commit a8518cce951629eaccde40fd0e51b36a5dc6321c)

ctripcorp/redis,ctripcorp/redis,ctripcorp/redis,ctripcorp/redis