Disable debuginfod in printer tests [BZ #28757]

With gdb-11.1-6.fc35.x86_64, I got

FAIL: nptl/test-cond-printers
FAIL: nptl/test-condattr-printers
FAIL: nptl/test-mutex-printers
FAIL: nptl/test-mutexattr-printers
FAIL: nptl/test-rwlock-printers
FAIL: nptl/test-rwlockattr-printers

$ cat nptl/test-condattr-printers.out
Error: Response does not match the expected pattern.
Command: start
Expected pattern: main
Response:  Temporary breakpoint 1 at 0x11d5: file test-condattr-printers.c, line 43.
Starting program: /export/build/gnu/tools-build/glibc-cet-gitlab/build-x86_64-linux/nptl/test-condattr-printers

This GDB supports auto-downloading debuginfo from the following URLs:
https://debuginfod.fedoraproject.org/


Enable debuginfod for this session? (y or [n])

Disable debuginfod to avoid GDB messages.  This fixes BZ #28757.

Reviewed-by: Florian Weimer <fweimer@redhat.com>