From this Jenkins upgrade (2.63) the configured JDK is no longer used by Jenkins builds: it is replaced at run time by JDK 1.8, but ONLY for Maven Projects.
For Free Style projects the behavior it right instead: Jenkins builds use the configured JDK (1.7).

Following the logs of Maven Projects:
Parsing POMs
Modules changed, recalculating dependency graph
Established TCP socket on 60215
maven3-agent.jar already up to date
maven3-interceptor.jar already up to date
maven3-interceptor-commons.jar already up to date
[CIT_BL] $ /home/jenkins/tools/hudson.model.JDK/JDK_1.7/bin/java -cp /home/jenkins/maven3-agent.jar:/home/jenkins/tools/hudson.tasks.Maven_MavenInstallation/MVN_3.0.5/boot/plexus-classworlds-2.4.jar org.jvnet.hudson.maven3.agent.Maven3Main /home/jenkins/tools/hudson.tasks.Maven_MavenInstallation/MVN_3.0.5 /home/jenkins/slave.jar /home/jenkins/maven3-interceptor.jar /home/jenkins/maven3-interceptor-commons.jar 60215
<===[JENKINS REMOTING CAPACITY]===>channel started
ERROR: ================================================================================
ERROR: Invalid project setup: jenkins/security/MasterToSlaveCallable : Unsupported major.minor version 52.0
ERROR: JENKINS-18403JENKINS-28294 JDK 'JDK 1.7' not supported to run Maven projects.
ERROR: Maven projects have to be launched with a Java version greater or equal to the minimum version required by the master.
ERROR: Use the Maven JDK Toolchains (plugin) to build your maven project with an older JDK.
ERROR: Retrying with slave Java and setting compile/test properties to point to /home/jenkins/tools/hudson.model.JDK/JDK_1.7.
ERROR: ================================================================================
Established TCP socket on 46450
maven3-agent.jar already up to date
maven3-interceptor.jar already up to date
maven3-interceptor-commons.jar already up to date
[CIT_BL] $ /usr/lib/jvm/java-8-oracle/jre/bin/java -cp /home/jenkins/maven3-agent.jar:/home/jenkins/tools/hudson.tasks.Maven_MavenInstallation/MVN_3.0.5/boot/plexus-classworlds-2.4.jar org.jvnet.hudson.maven3.agent.Maven3Main /home/jenkins/tools/hudson.tasks.Maven_MavenInstallation/MVN_3.0.5 /home/jenkins/slave.jar /home/jenkins/maven3-interceptor.jar /home/jenkins/maven3-interceptor-commons.jar 46450
<===[JENKINS REMOTING CAPACITY]===>channel started
FreeStyle log:
[src] $ /home/jenkins/tools/hudson.tasks.Maven_MavenInstallation/MVN_3.0.5/bin/mvn -f ./pom.xml -s /opt/maven_settings/settings_maven3.0.5.xml -Dmaven.test.skip=true -Dmaven.repo.local=/home/jenkins/workspace/CM/Build_SWITCH/.repository clean package -Pjboss,postgresql,noML,distribution -Ddb.owner=60363 -Ddistro-profile=app
[INFO] Scanning for projects...