TSAN summarising line was misplaced in get_core_dumps.sh

The line summarising TSAN reports was misplaced in the ASAN territory and thus never used. I also changed the variable name to be more TSAN-specific.

I:glue:exit status: 0
I:glue:stopping servers
I:glue:1 TSAN sanitizer report(s) found
D:/home/newman/isc/ws/bind9/bin/tests/system/glue:SUMMARY: ThreadSanitizer: data race (/home/newman/isc/ws/bind9/bin/named/.libs/named+0x42ecfd) (BuildId: 63d9d687e98418f4e6b1ca722138f598844bbd94) in check_lockfile
R:glue:FAIL
E:glue:2023-04-26T13:11:49+0200
FAIL: glue