qa/workunits/cephtool/test.sh: only include last line for epoch

qa/workunits/cephtool/test.sh: only include last line for epoch

/home/jenkins-build/build/workspace/ceph-pull-requests-arm64/qa/workunits/cephtool/test.sh:1606: test_mon_crush:  epoch='2017-06-20 04:44:52.862459 ffffad4d0200 -1 asok(0xffffa8000b10) AdminSocketConfigObs::init: failed: AdminSocket::bind_and_listen: The UNIX domain socket path /home/jenkins-build/build/workspace/ceph-pull-requests-arm64/build/src/test/td/t-7202/out/client.admin.48876.asok is too long! The maximum length on this system is 107
12'
/home/jenkins-build/build/workspace/ceph-pull-requests-arm64/qa/workunits/cephtool/test.sh:1607: test_mon_crush:  '[' '2017-06-20 04:44:52.862459 ffffad4d0200 -1 asok(0xffffa8000b10) AdminSocketConfigObs::init: failed: AdminSocket::bind_and_listen: The UNIX domain socket path /home/jenkins-build/build/workspace/ceph-pull-requests-arm64/build/src/test/td/t-7202/out/client.admin.48876.asok is too long! The maximum length on this system is 107
12' -gt 1 ']'
/home/jenkins-build/build/workspace/ceph-pull-requests-arm64/qa/workunits/cephtool/test.sh: line 1607: [: 2017-06-20 04:44:52.862459 ffffad4d0200 -1 asok(0xffffa8000b10) AdminSocketConfigObs::init: failed: AdminSocket::bind_and_listen: The UNIX domain socket path /home/jenkins-build/build/workspace/ceph-pull-requests-arm64/build/src/test/td/t-7202/out/client.admin.48876.asok is too long! The maximum length on this system is 107
12: integer expression expected

Signed-off-by: Kefu Chai <kchai@redhat.com>