Fix: tests: incorrect uri index

Fix: tests: incorrect uri index

Initial issue found by Coverity:

CID 1322864 (#1 of 1): Constant expression result
(CONSTANT_EXPRESSION_RESULT)impossible_and: The "and" condition size ==
2L && (uri + 0).dtype == LTTNG_DST_IPV4 && (uri + 0).utype ==
LTTNG_URI_DST && (uri + 0).stype == 0U && (uri + 0).port == 8989 &&
strcmp((uri + 0).subdir, "my/test/path") == 0 && strcmp((uri +
0).dst.ipv4, "127.0.0.1") == 0 && (uri + 1).dtype == LTTNG_DST_IPV4 &&
(uri + 1).utype == LTTNG_URI_DST && (uri + 1).stype == 0U && (uri +
1).port == 4242 && strcmp((uri + 0).subdir, "my/test/path") == 0 &&
strcmp((uri + 1).dst.ipv4, "127.0.0.1") == 0 can never be true because
(uri + 0).subdir cannot be equal to two different values at the same
time.

Review of the test source file led to further fixes.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>