fix(tests/spectre-meltdown-checker): pin due to bugs in tip

Pin back spectre-meltdown-checker.sh to previous working version due
to issues introduced in speed47/spectre-meltdown-checker#527 while
we're investigating them.

Signed-off-by: Riccardo Mancini <mancio@amazon.com>

Author: Manciukic

tests/integration_tests/security/test_vulnerabilities.py

@@ -17,7 +17,8 @@
 from framework.microvm import MicroVMFactory
 from framework.properties import global_props
 
-CHECKER_URL = "https://raw.githubusercontent.com/speed47/spectre-meltdown-checker/master/spectre-meltdown-checker.sh"
+# Pinned due to issues introduced in https://github.com/speed47/spectre-meltdown-checker/pull/527
+CHECKER_URL = "https://raw.githubusercontent.com/speed47/spectre-meltdown-checker/3a822fdcf291ebb8bfbcb77aa216ac342c6b2f12/spectre-meltdown-checker.sh"
 CHECKER_FILENAME = "spectre-meltdown-checker.sh"
 REMOTE_CHECKER_PATH = f"/tmp/{CHECKER_FILENAME}"
 REMOTE_CHECKER_COMMAND = f"sh {REMOTE_CHECKER_PATH} --no-intel-db --batch json"