There is some odd functionality/behavior in how the --test-suite
parameters interacts in conjunction with the 'test_suites' attribute in
the config file. If a user leaves an empty list underneath
'test_suites,' or if they negate the attribute entirely, even if said
user adds test suites via the --test-suite parameter, a schema violation
is thrown.

This patch mitigates this, by removing the schema requirement if the
user has indicated test suites within main.py parameters, allowing for
the 'test_suites' attribute to be optional.

Bugzilla ID: 1360
Signed-off-by: Nicholas Pratte <npratte@iol.unh.edu>