WIP Net::SMTPServer: switch from PreForkSimple to PreFork

spawns fewer fakesmtpd processes when they're not actually being used

XXX maybe we even want Fork rather than PreFork, need to do some
more testing...

cassandane/Cassandane/Net/SMTPServer.pm

@@ -5,15 +5,15 @@ use warnings;
 use Data::Dumper;
 use File::Spec::Functions qw(catfile);
 use File::Temp qw(mkstemps);
-use Net::Server::PreForkSimple;
+use Net::Server::PreFork;
 
 use lib ".";
 use Net::XmtpServer;
 use Cassandane::Util::Log;
 use Cassandane::Util::Slurp;
 use JSON;
 
-use base qw(Net::XmtpServer Net::Server::PreForkSimple);
+use base qw(Net::XmtpServer Net::Server::PreFork);
 
 sub new {
     my ($class, $params, @args) = @_;

cassandane/utils/fakesmtpd

@@ -25,7 +25,8 @@ my $smtpd = Cassandane::Net::SMTPServer->new({
     xmtp_personality => 'smtp',
     host => $host,
     port => $port,
-    max_servers => 3, # default is 50, yikes
+    min_servers => 1,
+    min_spare_servers => 0, # XXX not sure this has any useful effect vs 1
     control_file => "$basedir/conf/smtpd.json",
     xmtp_tmp_dir => "$basedir/tmp/",
     store_msg => 1,