core: Log local overrides as INFO rather than WARN

A user has at some point explicitly specified in .terraformrc that
overriding should take place (unlike PATH based overrides), so this
should log as INFO rather than WARN.

It is still of value for debugging purposes, however!

config.go

@@ -170,7 +170,7 @@ func (c1 *Config) Merge(c2 *Config) *Config {
 	}
 	for k, v := range c2.Providers {
 		if v1, ok := c1.Providers[k]; ok {
-			log.Printf("[WARN] Local %s provider configuration '%s' overrides '%s'", k, v, v1)
+			log.Printf("[INFO] Local %s provider configuration '%s' overrides '%s'", k, v, v1)
 		}
 		result.Providers[k] = v
 	}
@@ -179,7 +179,7 @@ func (c1 *Config) Merge(c2 *Config) *Config {
 	}
 	for k, v := range c2.Provisioners {
 		if v1, ok := c1.Provisioners[k]; ok {
-			log.Printf("[WARN] Local %s provisioner configuration '%s' overrides '%s'", k, v, v1)
+			log.Printf("[INFO] Local %s provisioner configuration '%s' overrides '%s'", k, v, v1)
 		}
 		result.Provisioners[k] = v
 	}