Change default LaunchCommandsFactoryBean main command

Instead of assuming java is in a system path, use JAVA_HOME
as a prefix for /bin/java. Change test to use master-runner
instead of low level master-command. It should be safe to assume
that atleast JAVA_HOME is set.
Fixing test due to previous change for LaunchCommandsFactoryBean
Adding failure reason for appmaster status assert

In case app submission fails we may get the actual
reason from Appmaster.stderr file. Try to read that file
and pass it to assert as a failure reason.