Fix SNMP latency to exclude Slim instance creation overhead

Move time measurement to only capture the actual SNMP GET request,
excluding the Slim() context manager initialization.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

checkers/snmp.py

@@ -66,7 +66,6 @@ class SnmpChecker(BaseChecker):
         temperature_oid = self.config.get("temperature_oid")
         timeout_val = self.config.get("timeout", 5)
 
-        start = time.time()
         try:
             with Slim() as slim:
                 # Construit la liste des OIDs à interroger
@@ -74,6 +73,7 @@ class SnmpChecker(BaseChecker):
                 if temperature_oid:
                     oids.append(ObjectType(ObjectIdentity(temperature_oid)))
 
+                start = time.time()
                 error_indication, error_status, error_index, var_binds = await slim.get(
                     community,
                     host,
@@ -82,7 +82,6 @@ class SnmpChecker(BaseChecker):
                     timeout=timeout_val,
                     retries=1
                 )
-
                 response_time = (time.time() - start) * 1000  # ms
 
             if error_indication: