osmo-gsm-tester: jenkins fixes: install JDK, SSH instructions

Add instructions to install Java JDK for jenkins build slave.
Minor fixes to SSH key instructions.

Change-Id: Ib2c1adc2ddee3be016e4d253451593b19dbe133a
diff --git a/doc/manuals/chapters/install.adoc b/doc/manuals/chapters/install.adoc
index b703498..0c69dcd 100644
--- a/doc/manuals/chapters/install.adoc
+++ b/doc/manuals/chapters/install.adoc
@@ -64,6 +64,15 @@
 useradd -m jenkins
 ----
 
+==== Install Java on Main Unit
+
+To be able to launch the Jenkins build slave, a Java RE must be available on
+the main unit. For example:
+
+----
+apt-get install default-jdk
+----
+
 ==== Allow SSH Access from Jenkins Master
 
 Create an SSH keypair to be used for login on the osmo-gsm-tester. This may be
@@ -73,6 +82,7 @@
 
 ----
 # su jenkins
+$ mkdir -p /usr/local/jenkins/keys
 $ ssh-keygen
 Generating public/private rsa key pair.
 Enter file in which to save the key (/home/jenkins/.ssh/id_rsa): /usr/local/jenkins/keys/osmo-gsm-tester-rnd
@@ -122,7 +132,7 @@
 ----
 su jenkins
 main_unit_ip=10.9.8.7
-ssh jenkins@$main_unit_ip
+ssh -i /usr/local/jenkins/keys/osmo-gsm-tester-rnd jenkins@$main_unit_ip
 exit
 ----