[9.20] fix: dev: Use CMM_{STORE,LOAD}_SHARED to store/load glue in gluelist

ThreadSanitizer has trouble understanding that gluelist->glue is
constant after it is assigned to the slabheader with cmpxchg.  Help
ThreadSanitizer to understand the code by using CMM_STORE_SHARED and
CMM_LOAD_SHARED on gluelist->glue.

Backport of MR !9929

Merge branch 'backport-ondrej/hint-tsan-in-addglue-9.20' into 'bind-9.20'

See merge request isc-projects/bind9!9936