Cli output of some tests contains only "0: " (instead of correct result)

Description of problem:
Cli output of some tests in wildfly core contains only "0: " (instead of correct result)

How reproducible:
66% on RHEL && IBM JDK 8

Affected tests found so far:

• org.jboss.as.test.manualmode.vault.VaultPasswordsInCLITestCase#testWrongVaultPassword

  • java.lang.AssertionError: Password should be wrong
    Expected: a string containing "Keystore was tampered with, or password was incorrect"
         but: was "0: "
    	at org.hamcrest.MatcherAssert.assertThat(MatcherAssert.java:20)
    	at org.junit.Assert.assertThat(Assert.java:865)
    	at org.jboss.as.test.manualmode.vault.VaultPasswordsInCLITestCase.testWrongVaultPassword(VaultPasswordsInCLITestCase.java:135)

• org.jboss.as.test.manualmode.vault.VaultPasswordsInCLITestCase#testRightVaultPassword

  • java.lang.AssertionError: Password should be right and authentication successful
    Expected: a string containing "\"outcome\" => \"success\""
         but: was "0: "
    	at org.hamcrest.MatcherAssert.assertThat(MatcherAssert.java:20)
    	at org.junit.Assert.assertThat(Assert.java:865)
    	at org.jboss.as.test.manualmode.vault.VaultPasswordsInCLITestCase.testRightVaultPassword(VaultPasswordsInCLITestCase.java:148)

• org.wildfly.core.test.standalone.mgmt.HTTPSConnectionWithCLITestCase#testTrustedCLICertificate
• org.jboss.as.test.manualmode.management.cli.CustomVaultInCLITestCase#testWrongVaultPassword

Steps to Reproduce:

1. mvn install -Dts.manualmode -fae -Dmaven.test.failure.ignore=true -Dnode0=$MYTESTIP_1 -DfailIfNoTests=false -Dtest=VaultPasswordsInCLITestCase