VM plugin improvements

Fix most of the previous reports on the VM plugin. Now the output is much better and more consistent:

    $ scripts/avocado run --vm-domain fedora20 --vm-hostname 192.168.122.30 --vm-username autotest --vm examples/tests/sleeptest.py examples/tests/failtest.py
    VM DOMAIN : fedora20
    VM LOGIN  : autotest@192.168.122.30
    JOB ID    : 60ddd718e7d7bb679f258920ce3c39ce73cb9779
    JOB LOG   : /home/lmr/avocado/job-results/job-2014-09-16T18.41-60ddd71/job.log
    TESTS     : 2
    (1/2) examples/tests/sleeptest.py: PASS (1.00 s)
    (2/2) examples/tests/failtest.py: FAIL (0.00 s)
    PASS      : 1
    ERROR     : 0
    NOT FOUND : 0
    FAIL      : 1
    SKIP      : 0
    WARN      : 0
    TIME      : 1.01 s