Add UI option to control when update email is sent

https://github.com/webmin/webmin/issues/2726

package-updates/index.cgi

@@ -220,6 +220,13 @@ else {
 	}
 print &ui_table_row($text{'index_email'}, $efield);
 
+# When to send email
+print &ui_table_row($text{'index_ewhen'},
+	&ui_radio("when", int($config{'sched_when'}),
+		  [ [ 0, $text{'index_ewhen0'} ],
+		    [ 1, $text{'index_ewhen1'} ],
+		    [ 2, $text{'index_ewhen2'} ] ]));
+
 # Install or just notify?
 $action_ui = &ui_select("action", int($config{'sched_action'}),
 			[ [ -1, $text{'index_action-1'} ],

package-updates/lang/en

@@ -19,6 +19,10 @@ index_schedd=day
 index_schedw=week
 index_email=Email updates report to
 index_email_def=Webmin default ($1)
+index_ewhen=Send email when
+index_ewhen0=Any update is installed
+index_ewhen1=Any update failed
+index_ewhen2=Never (but still install updates)
 index_action=Action when update needed
 index_action-1=Just notify for security updates
 index_action0=Just notify for any updates

package-updates/save_sched.cgi

@@ -6,6 +6,7 @@ require './package-updates-lib.pl';
 
 &lock_file($module_config_file);
 $config{'sched_email'} = $in{'email_def'} ? '*' : $in{'email'};
+$config{'sched_when'} = $in{'when'};
 $config{'sched_action'} = $in{'action'};
 &save_module_config();
 &unlock_file($module_config_file);

package-updates/update.pl

@@ -33,6 +33,7 @@ else {
 	}
 &start_update_progress([ map { $_->{'name'} } @todo ]);
 $icount = 0;
+$fcount = 0;
 foreach $t (@todo) {
 	next if ($already{$t->{'update'}});
 	my $umsg = $t->{'security'} ? "security update" : "update";
@@ -57,6 +58,7 @@ foreach $t (@todo) {
 			$body .= "However, this $umsg could not be installed! ".
 				 "Try the update manually\nusing the Package ".
 				 "Updates module.\n\n";
+			$fcount++;
 			}
 		foreach $p (@$done) {
 			$already{$p}++;
@@ -89,7 +91,9 @@ if ($tellcount) {
 # Email the admin
 $emailto = $config{'sched_email'} eq '*' ? $gconfig{'webmin_email_to'}
 					 : $config{'sched_email'};
-if ($emailto && $body) {
+if ($emailto && $body &&
+    ($config{'sched_when'} == 0 ||
+     $config{'sched_when'} == 1 && $fcount)) {
 	&foreign_require("mailboxes", "mailboxes-lib.pl");
 	my $from = &mailboxes::get_from_address();
 	my $mail = { 'headers' =>