Javadoc generation definitely not thread safe in travis

.travis.yml

@@ -54,7 +54,7 @@ before_script:
   - echo "<settings><servers><server><id>ossrh</id><username>\${env.OSSRH_USER}</username><password>\${env.OSSRH_PASS}</password></server><server><id>netbeans</id></server></servers><profiles><profile><id>deployment</id><properties><keystore.password>\${env.KEYSTORE_PASSWD}</keystore.password><gpg.passphrase>\${env.GPG_PASSPHRASE}</gpg.passphrase></properties></profile></profiles></settings>" > ~/settings.xml
 
 script:
-  - if [ "$TRAVIS_OS_NAME" == "linux" ]; then travis_retry mvn -T 2 --batch-mode --settings ~/settings.xml -Djava.awt.headless=true -Dgpg.defaultKeyring=false -Dgpg-keyname=1481F619 -Dgpg.publicKeyring=src/travis/pubring.gpg -Dgpg.secretKeyring=src/travis/secretring.gpg clean deploy -P deployment,create-modules,create-sources,create-javadoc,create-autoupdate,replace-windows-icon,create-exe,create-targz;fi
+  - if [ "$TRAVIS_OS_NAME" == "linux" ]; then travis_retry mvn --batch-mode --settings ~/settings.xml -Djava.awt.headless=true -Dgpg.defaultKeyring=false -Dgpg-keyname=1481F619 -Dgpg.publicKeyring=src/travis/pubring.gpg -Dgpg.secretKeyring=src/travis/secretring.gpg clean deploy -P deployment,create-modules,create-sources,create-javadoc,create-autoupdate,replace-windows-icon,create-exe,create-targz;fi
   - if [ "$TRAVIS_OS_NAME" == "osx" ]; then travis_retry mvn --batch-mode --settings ~/settings.xml -Djava.awt.headless=true -Dgpg.defaultKeyring=false -Dgpg-keyname=1481F619 -Dgpg.publicKeyring=src/travis/pubring.gpg -Dgpg.secretKeyring=src/travis/secretring.gpg clean deploy -P deployment,create-dmg;fi
   - if [ "$TRAVIS_OS_NAME" == "linux" -a "$TRAVIS_BRANCH" == "master" -a "$TRAVIS_PULL_REQUEST" == "false" ]; then mvn versioneye:update; fi