MINOR: checks: use check->state instead of srv->state & SRV_CHECKED

Having the check state partially stored in the server doesn't help.
Some functions such as srv_getinter() rely on the server being checked
to decide what check frequency to use, instead of relying on the check
being configured. So let's get rid of SRV_CHECKED and SRV_AGENT_CHECKED
and only use the check's states instead.
diff --git a/src/cfgparse.c b/src/cfgparse.c
index b675941..98d4c67 100644
--- a/src/cfgparse.c
+++ b/src/cfgparse.c
@@ -5124,7 +5124,6 @@
 			}
 
 			newsrv->check.state |= CHK_ST_CONFIGURED | CHK_ST_ENABLED;
-			newsrv->state |= SRV_CHECKED;
 		}
 
 		if (do_agent) {
@@ -5147,7 +5146,6 @@
 			}
 
 			newsrv->agent.state |= CHK_ST_CONFIGURED | CHK_ST_ENABLED;
-			newsrv->state |= SRV_AGENT_CHECKED;
 		}
 
 		if (!defsrv) {
@@ -7018,7 +7016,7 @@
 					goto next_srv;
 				}
 
-				if (!(srv->state & SRV_CHECKED)) {
+				if (!(srv->check.state & CHK_ST_CONFIGURED)) {
 					Alert("config : %s '%s', server '%s': unable to use %s/%s for "
 						"tracking as it does not have checks enabled.\n",
 						proxy_type_str(curproxy), curproxy->id,