virttest.utils_misc: Add functions to get open fds

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
virttest.standalone_test: Add open_fd param to stdout functions

So that we can print how many open file descriptors (fds)
virt-test has at the end of each step of execution.

By default, it's disabled, will be controlled by a test
runner flag in a later patch.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
run: Add debug section and --show-open-fd option

It is very useful from time to time to show the number
of open fds at the end of each virt-test directory. So
add a debug session for debug related options, and also
add the --show-open-fd option that will give you the
following nice output:

$ ./run -t qemu --show-open-fd
Running setup. Please wait...
SETUP: PASS (13.82 s) (5 fd)
DATA DIR: /home/lmr/virt_test
DEBUG LOG: /home/lmr/Code/virt-test.git/logs/run-2014-01-31-18.07.40/debug.log
TESTS: 10
(1/10) type_specific.io-github-autotest-qemu.migrate.default.tcp: PASS (42.54 s) (12 fd)
...

Making it very easy to verify if virt-test is leaking
fds or not at the end of each test.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
Merge pull request #1422 from autotest/get_open_fds

Get open fds