tests: avoid too-large constants

tests: avoid too-large constants

Compiling with gcc 4.1.2 (RHEL 5) on a 32-bit platform complains:

virdbustest.c: In function 'testMessageSimple':
virdbustest.c:61: warning: integer constant is too large for 'long' type
virdbustest.c:62: warning: integer constant is too large for 'long' type
virdbustest.c: In function 'testMessageArray':
virdbustest.c:183: warning: this decimal constant is unsigned only in ISO C90
virdbustest.c: In function 'testMessageStruct':
virdbustest.c:239: warning: integer constant is too large for 'long' type
virdbustest.c:240: warning: integer constant is too large for 'long' type

* tests/virdbustest.c (testMessageSiple, testMessageArray)
(testMessageStruct): Don't violate C89 constant constraints.

Signed-off-by: Eric Blake <eblake@redhat.com>