azure-run-tests: handle single unexpanded parameter too
    
    If TESTS_TO_RUN contains a single parameter that cannot be expanded,
    bash will not perform brace elimination. Remove braces manually.
    
    For example, TESTS_TO_RUN='test_xmlrpc/test_*.py' will not expand
    outside of ipatests and the script would generate
    
     tests_to_run=-k{test_xmlrpc/test_*.py}
    
    Braces then will prevent actual ipa-run-tests execution from matching
    any of XMLRPC tests.
    
    Reviewed-By: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>