run_tests.sh usage message and behavior for -x don't match

[Eric Harney]

run_tests.sh's usage message says that -x is to "Stop running tests after the first error" but it actually is translated to --coverage-xml. Either need to update the message or continue passing -x to nose.

[Rushi Agrawal (rushiagr)]

This commit
https://github.com/openstack/cinder/commit/50792c2ff41fdc7e73b3e3c51f4510366debfd14
shows that the committer wanted to introduce an option for XML coverage report, but unknowingly overrode the default option for nose tests: -x.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/15630

[Rushi Agrawal (rushiagr)]

The same bug can exist in other OpenStack projects too.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/15630
Committed: http://github.com/openstack/cinder/commit/eedc857008a122ee38661581f27f102de52a4886
Submitter: Jenkins
Branch: master

commit eedc857008a122ee38661581f27f102de52a4886
Author: Rushi Agrawal <email address hidden>
Date: Sat Nov 3 12:21:28 2012 +0530

    Fix run_tests.sh ambiguous usage msg and behaviour for -x option

    In commit
    https://github.com/openstack/cinder/commit/
    50792c2ff41fdc7e73b3e3c51f4510366debfd14,
    the committer wanted to add an option in run_tests.sh for generating XML
    coverage report, but ended up accidentally overriding the default nose
    option -x. But, the usage message still showed that using option -x will
    'Stop running tests after the first error or failure'. So, I changed the
    option to generate XML report to -X (capitalized 'x'). So now both -x and
    -X options are available, with different purposes.

    Fixes bug 1070047

    Change-Id: Ie8c30c14629d4811d6db74f3eea9cdecb1d27c8a