Remove unset( $jenkins_job_name ) from entry point

this variable is undefined.

in the past, to add extra phpunit arguments, we added
$jenkins_job_name = getenv( 'JOB_NAME' );

we are not setting it now like that so it's pointless
to unset it.

Change-Id: I0299ac285f089861ee2adbbde4804bcc500747e4
Merge "Remove unset( $jenkins_job_name ) from entry point"