change the TEST_LEVEL to default in jenkinsfile

[alexyiuxmos]

No description provided.

[xross]

Hi Alex, the idea here is that we have multiple test levels with Jenkins setting TEST_LEVEL appropriately (if this is not working let me know, we need to update https://github.com/xmos/jenkins-dsl/blob/develop/jenkins_jobs/jcim/jenkinsfiles/weekdays and https://github.com/xmos/jenkins-dsl/blob/develop/jenkins_jobs/jcim/jenkinsfiles/weekends)

prs: smoke
nightly: default/normal
weekend: extended

for a small libs like sdram I suspect all tests can run all the time.