AMBARI-14778. Ambari Server CA should use sha265 as default message digest algorthm (rlevas)

ambari-server/conf/unix/ca.config

@@ -10,7 +10,7 @@ serial                 = $dir/serial
 default_days           = 365    
 
 default_crl_days       = 7  
-default_md             = md5 
+default_md             = sha256
 
 policy                 = policy_anything 
 

ambari-server/conf/windows/ca.config

@@ -10,7 +10,7 @@ serial                 = $dir\\serial
 default_days           = 365
 
 default_crl_days       = 7
-default_md             = md5
+default_md             = sha256
 
 policy                 = policy_anything