tests: fix compile warning of tests/test-ovsdb.c

tests: fix compile warning of tests/test-ovsdb.c

This patch fixed the following compile warning:

tests/test-ovsdb.c: In function 'do_evaluate_conditions':
tests/test-ovsdb.c:744: warning: format '%2d' expects type 'int', but argument 2 has type 'size_t'
tests/test-ovsdb.c: In function 'do_execute_mutations':
tests/test-ovsdb.c:850: warning: format '%2d' expects type 'int', but argument 2 has type 'size_t'
tests/test-ovsdb.c: In function 'do_query':
tests/test-ovsdb.c:972: warning: format '%2d' expects type 'int', but argument 2 has type 'size_t'
tests/test-ovsdb.c: In function 'do_query_distinct':
tests/test-ovsdb.c:1105: warning: format '%2d' expects type 'int', but argument 2 has type 'size_t'
tests/test-ovsdb.c: In function 'parse_uuids':
tests/test-ovsdb.c:1600: warning: format '%d' expects type 'int', but argument 2 has type 'size_t'

Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>