Fix coverage option for run_tests.sh

This commit fixes run_tests.sh so that when the -c flag is specified
coverage will actually be collected. Previously the --coverage option
was added to testrargs, however this isn't a testr flag. It is used by
pbr to wrap testr with coverage start and coverage report. This changes
run_tests() so that when coverage is specified it runs the unit tests
using setup.py so that the coverage flag can be used.

Change-Id: Iad0d508b6a4638a67e45646148144f627588fa48
Separate negative tests for test_multiple_create

Move negative tests from test_multiple_create.py to
test_multiple_create_negative.py.

Partially implements blueprint negative-test-files

Change-Id: I413d02356f2c3f578c01a6e2e7beb953576c4015
Separate negative tests for test_projects

Move negative tests from test_projects.py to test_projects_negative.py

Partially implements blueprint negative-test-files

Change-Id: I37d3eb8f30ec0101a2abc3f3ca71d191ea1c7fa6
Scenario : Start instances using fixed network when possible

Uses the fixed_network_name option to select which network
to boot test instances on.  This allows Tempest to be run
in environments where there are multiple networks available.

Change-Id: I64ad6ce6bee3fe33537ac4f8d8d913856fe46554
Partial-Bug: #1250866
Removal of methods from json/xml network_client files

Remove create_security_group, create_security_group_rule
from "json/network_client.py" and "xml/network_client.py"
and instead use "_creater"/"_updater" from "network_client_base.py"

Change-Id: I2f0b16ea832fe0704869a9d778a8d3ed518090cc
Merge "Removal of methods from json/xml network_client files"
Merge "Separate negative tests for test_projects"
Merge "Scenario : Start instances using fixed network when possible"
Merge "Fix coverage option for run_tests.sh"
Merge "Separate negative tests for test_multiple_create"
Merge branch 'master' of https://github.com/openstack/tempest