BUG/MINOR: samples: add missing context names for sample fetch functions

In 2.4, two commits added support for supporting sample fetch calls from
new config and CLI contexts, but these were not added to the visibile
names, which may possibly cause "(null)" to appear in some error messages.
The commit in question were:
  db5e0dbea ("MINOR: sample: add a new CLI_PARSER context for samples")
  f9a7a8fd8 ("MINOR: sample: add a new CFG_PARSER context for samples")

This patch needs to be backported where these are present (2.4 and above).
diff --git a/src/sample.c b/src/sample.c
index 63816be..7db5fde 100644
--- a/src/sample.c
+++ b/src/sample.c
@@ -327,6 +327,8 @@
 	[SMP_CKP_FE_HRS_BDY] = "frontend http-response body rule",
 	[SMP_CKP_FE_LOG_END] = "logs",
 	[SMP_CKP_BE_CHK_RUL] = "backend tcp-check rule",
+	[SMP_CKP_CFG_PARSER] = "configuration parser",
+	[SMP_CKP_CLI_PARSER] = "CLI parser",
 };
 
 /* This function returns the type of the data returned by the sample_expr.