MINOR: httpclient: rename dash by dot in global option

Rename the httpclient-ssl-verify into httpclient.ssl.verify.
diff --git a/src/http_client.c b/src/http_client.c
index ca55c02..c21786a 100644
--- a/src/http_client.c
+++ b/src/http_client.c
@@ -1273,7 +1273,7 @@
 }
 
 static struct cfg_kw_list cfg_kws = {ILH, {
-	{ CFG_GLOBAL, "httpclient-ssl-verify", httpclient_parse_global_verify },
+	{ CFG_GLOBAL, "httpclient.ssl.verify", httpclient_parse_global_verify },
 	{ 0, NULL, NULL },
 }};