cmake: disable LeakSanitizer suppression output to fix CLI tests

cmake: disable LeakSanitizer suppression output to fix CLI tests

LeakSanitizer prints matched suppressions by default, which causes CLI
tests to fail when built with LSan enabled. The tests compare actual
output against expected output, and the additional LSan messages break
this comparison.

Example failure:

```
/home/jenkins-build/build/workspace/ceph-pull-requests/src/test/cli/ceph-kvstore-tool/help.t: failed
--- /home/jenkins-build/build/workspace/ceph-pull-requests/src/test/cli/ceph-kvstore-tool/help.t
+++ /home/jenkins-build/build/workspace/ceph-pull-requests/src/test/cli/ceph-kvstore-tool/help.t.err
@@ -21,3 +21,9 @@
     stats
     histogram [prefix]

+  -----------------------------------------------------
+  Suppressions used:
+    count      bytes template
+        1         45 ^MallocExtension::Initialize
+  -----------------------------------------------------
+
```

Set LSAN_OPTIONS=print_suppressions=0 to prevent this output rather
than modifying test expectations, since the suppression messages are
not part of the actual tool output and would vary between builds.

This change should fix run_cli_tests failures when building with LeakSanitizer

See https://github.com/google/sanitizers/wiki/SanitizerCommonFlags
for the environment variables respected by LeakSanitizer.

Signed-off-by: Kefu Chai <tchaikov@gmail.com>