SonarQube Jenkins Plugin won't authenticate to Artifactory - maven

Question

SonarQube 5.1 running on Ubuntu 12.04.4 LTS
Jenkins ver. 1.616 running on Ubuntu 12.04.4 LTS
SonarQube Plugin 2.2.1
Artifactory Pro Power Pack 3.8.0 (rev. 30190) running on Ubuntu 12.04.5 LTS
sbt 0.13.8
Apache Maven 3.0.4
Maven home: /usr/share/maven
Java version: 1.8.0_45, vendor: Oracle Corporation
Java home: /usr/lib/jvm/jdk1.8.0_45/jre
Default locale: en_US, platform encoding: UTF-8
OS name: "linux", version: "3.5.0-23-generic", arch: "amd64", family: "unix"
Attempting to use the SonarQube Jenkins Plugin in a Jenkins Build, the plugin seems to try to rebuild the entire build and re-resolve all the dependencies out of Artifactory. Problem is, unlike the rest of the build, when the SonarQube plugin requests artifacts from Artifactory, it does so as a non-authenticated-user, and Artifactory refuses the request.
I've tried everything from copying the <servers/>, <profiles/>, and <activeProfiles/> from the jenkins user's settings.xml file into /etc/maven.settings.xml and explicitly telling the plugin to use the former as user settings and the latter as system settings - in short, anything and everything I could find documented to medieval brute force the plugin to use the jenkins user's credentials , but still it just keeps connecting as a non-authenticated user and having its requests refused.
Example from Jenkins Log (sensitive information obfuscated):
INFO: No credentials available for BASIC 'Artifactory Realm'#libs.<organization>;:443
[WARNING] Could not transfer metadata <GAV>/maven-metadata.xml from/to ArtifactorySnapshotsRepo (<Artifactory URL>/artifactory/libs-snapshot/): Not authorized.
[WARNING] The POM for org.codehaus.jackson:jackson-core-asl:jar:1.8 is missing, no dependency information available
[WARNING] The POM for org.codehaus.jackson:jackson-mapper-asl:jar:1.8 is missing, no dependency information available
[WARNING] Failure to transfer <GAV>/maven-metadata.xml from <Artifactory URL>/artifactory/libs-snapshot/ was cached in the local repository, resolution will not be reattempted until the update interval of ArtifactorySnapshotsRepo has elapsed or updates are forced. Original error: Could not transfer metadata <GAV>/maven-metadata.xml from/to ArtifactorySnapshotsRepo (<Artifactory URL>/artifactory/libs-snapshot/): Not authorized.
And in Artifactory's request.log we get (again with sensitive information obfuscated):
20150916190344|5181|REQUEST|<Jenkins IP>;|non_authenticated_user|GET|/libs-snapshot//<GAV>/maven-metadata.xml|HTTP/1.0|401|0
The maven command launched by the SonarQube Plugin was as follows (lines broken for clarity, sensitive information obfuscated):
mvn
-f /var/lib/jenkins/workspace/NE-BUILD-1/pom.xml
-s /var/lib/jenkins/.m2/settings.xml
-gs /etc/maven/settings.xml
-e
-B org.codehaus.mojo:sonar-maven-plugin:2.6:sonar
-Dsonar.jdbc.url=jdbc:postgresql://<server>:<port>/sonar
******** ********
-Dsonar.host.url=http://<server>:<port>/
-Dsonar.branch=sbt-publish-deb ******** ********
How can I make this process authenticate to Artifactory properly?