Description of problem:
Some change in the testing version causes rlRun -s being stuck in an endless loop under some circumstances. I guess the culprit is commit 688273145292c75fb3e5ea013621746bd713086d.

Version-Release number of selected component (if applicable):
beakerlib-1.13-1.el7eso.noarch

How reproducible:
always

Steps to Reproduce:
# cat loop.sh
#!/bin/bash

. /usr/share/beakerlib/beakerlib.sh || exit 1

function sleep() {
    rlLogInfo "Waiting $1 secs"
    /bin/sleep $1
}

rlJournalStart
    rlPhaseStart FAIL
        rlRun -s "systemd-run --scope ./test.sh" 
    rlPhaseEnd
rlJournalEnd

# cat test.sh
#!/bin/bash

echo "Forking sleep"
( echo "Forked"; while true; do sleep 1; done ) &
echo "Main end"

Actual results:
# bash loop.sh 

::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
:: [   LOG    ] :: Phase of FAIL type
::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

:: [  BEGIN   ] :: Running 'systemd-run --scope ./test.sh'
Running scope as unit run-18865.scope.
Forking sleep
Main end
Forked
:: [ 07:39:06 ] :: [ INFO    ] :: Waiting 0.01 secs
:: [ 07:39:06 ] :: [ INFO    ] :: Waiting 0.01 secs
:: [ 07:39:06 ] :: [ INFO    ] :: Waiting 0.01 secs
:: [ 07:39:06 ] :: [ INFO    ] :: Waiting 0.01 secs
:: [ 07:39:06 ] :: [ INFO    ] :: Waiting 0.01 secs
:: [ 07:39:06 ] :: [ INFO    ] :: Waiting 0.01 secs
:: [ 07:39:06 ] :: [ INFO    ] :: Waiting 0.01 secs
:: [ 07:39:06 ] :: [ INFO    ] :: Waiting 0.01 secs
:: [ 07:39:06 ] :: [ INFO    ] :: Waiting 0.01 secs
:: [ 07:39:06 ] :: [ INFO    ] :: Waiting 0.01 secs
:: [ 07:39:06 ] :: [ INFO    ] :: Waiting 0.01 secs (# see testing.sh:799)
...

Expected results:
# rpm -q beakerlib
beakerlib-1.11-1.el7.noarch
# bash loop.sh 

::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
:: [   LOG    ] :: Phase of FAIL type
::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

:: [  BEGIN   ] :: Running 'systemd-run --scope ./test.sh'
Running scope as unit run-19470.scope.
Forking sleep
Main end
Forked
:: [   PASS   ] :: Command 'systemd-run --scope ./test.sh' (Expected 0, got 0)
:: [ 07:40:34 ] :: JOURNAL XML: /var/tmp/beakerlib-h11RGSv/journal.xml
:: [ 07:40:34 ] :: JOURNAL TXT: /var/tmp/beakerlib-h11RGSv/journal.txt