ovsdb-idl: fix compile warning of lib/ovsdb-idl.c

ovsdb-idl: fix compile warning of lib/ovsdb-idl.c

This patch fixed the following compile warning:

lib/ovsdb-idl.c: In function 'ovsdb_idl_txn_process_inc_reply':
lib/ovsdb-idl.c:1524: warning: format '%u' expects type 'unsigned int', but argument 5 has type 'size_t'
lib/ovsdb-idl.c:1538: warning: format '%ld' expects type 'long int', but argument 5 has type 'long long int'
lib/ovsdb-idl.c:1550: warning: format '%u' expects type 'unsigned int', but argument 5 has type 'size_t'
lib/ovsdb-idl.c: In function 'ovsdb_idl_txn_process_insert_reply':
lib/ovsdb-idl.c:1579: warning: format '%u' expects type 'unsigned int', but argument 5 has type 'size_t'

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