Tune gerrit parameters.

In order to clone 8 keystone repos simultaneously via https in dev,
the following were needed:

httpd.acceptorThreads>=4
sshd.threads>=8

And database.poolLimit is supposed to be higher than http+ssh threads.

Change-Id: I8d011af41e32f7865424d54d5a78a10a3689e708

modules/gerrit/templates/gerrit.config.erb

@@ -9,6 +9,7 @@
 	hostname = localhost
 	database = reviewdb
 	username = gerrit2
+	poolLimit = 20
 [auth]
 	type = OPENID_SSO
 	openIdSsoUrl = <%= openidssourl %>
@@ -21,8 +22,10 @@
 	javaHome = /usr/lib/jvm/java-6-openjdk/jre
 [sshd]
 	listenAddress = *:29418
+	threads = 12
 [httpd]
 	listenUrl = proxy-https://*:8081/
+	acceptorThreads = 8
 [cache]
 	directory = cache
 [cache "web_sessions"]