Fixes: ceph#14190

when user passes bad parameter(e.g. pass "null" to bool parameter), the ceph_json.cc::decode_json_obj()
will raise a exception with type of JSONDecoder::err(). If we do not catch this exception, the radosgw
server will abort.

$ curl -X PUT http://ceph1:9090/admin/metadata?user&format=json -d 'data = { "mtime": "null"}'

terminate called after throwing an instance of 'JSONDecoder::err'
*** Caught signal (Aborted) **
 in thread 7ff982f55700
 ceph version 10.0.1-787-gc485d29 (c485d29)
 1: (ceph::BackTrace::BackTrace(int)+0x2d) [0x7ffa814db8c5]
 2: (()+0x8fbfb7) [0x7ffa814dafb7]
 3: (()+0xf100) [0x7ffa758a6100]
 4: (gsignal()+0x37) [0x7ffa748e05f7]
 5: (abort()+0x148) [0x7ffa748e1ce8]
 6: (__gnu_cxx::__verbose_terminate_handler()+0x165) [0x7ffa751e49b5]
 7: (()+0x5e926) [0x7ffa751e2926]
 8: (()+0x5e953) [0x7ffa751e2953]
 9: (()+0x5eb73) [0x7ffa751e2b73]
 10: (bool JSONDecoder::decode_json<long>(char const*, long&, JSONObj*, bool)+0x28c) [0x7ffa8135920a]
 11: (RGWMetadataManager::put(std::string&, ceph::buffer::list&, RGWMetadataHandler::sync_type_t, obj_version*)+0x173) [0x7ffa81468029]
 12: (RGWOp_Metadata_Put::execute()+0x172) [0x7ffa81308dcc]
 13: (()+0x7532d2) [0x7ffa813322d2]
 14: (RGWFCGXProcess::handle_request(RGWRequest*)+0x90) [0x7ffa813328a4]

Reported-by: Coffee Chou <coffee.zyr@gmail.com>
Signed-off-by: Dunrong Huang <riegamaths@gmail.com>

when user passes bad parameter(e.g. pass "null" to bool parameter), the ceph_json.cc::decode_json_obj()
will raise a exception with type of JSONDecoder::err(). If we do not catch this exception, the radosgw
server will abort.

Fixes: ceph#14191

$ curl -X PUT http://ceph1:9090/admin/user?quota&uid=test5&quota-type=user -d '{"enabled": "null"}'

 0> 2015-12-28 11:25:20.864091 7f0d46fb5700 -1 *** Caught signal (Aborted) **
 in thread 7f0d46fb5700

 ceph version 10.0.1-787-gc485d29 (c485d29)
 1: (ceph::BackTrace::BackTrace(int)+0x2d) [0x7f0e13ef88c5]
 2: (()+0x8fbfb7) [0x7f0e13ef7fb7]
 3: (()+0xf100) [0x7f0e082c3100]
 4: (gsignal()+0x37) [0x7f0e072fd5f7]
 5: (abort()+0x148) [0x7f0e072fece8]
 6: (__gnu_cxx::__verbose_terminate_handler()+0x165) [0x7f0e07c019b5]
 7: (()+0x5e926) [0x7f0e07bff926]
 8: (()+0x5e953) [0x7f0e07bff953]
 9: (()+0x5eb73) [0x7f0e07bffb73]
 10: (bool JSONDecoder::decode_json<bool>(char const*, bool&, JSONObj*, bool)+0x288) [0x7f0e13d74c2c]
 11: (RGWQuotaInfo::decode_json(JSONObj*)+0x6c) [0x7f0e13d71128]
 12: (void decode_json_obj<RGWQuotaInfo>(RGWQuotaInfo&, JSONObj*)+0x23) [0x7f0e13d21f16]
 13: (int rgw_rest_get_json_input<RGWQuotaInfo>(CephContext*, req_state*, RGWQuotaInfo&, int, bool*)+0x11e) [0x7f0e13d21e48]
 14: (RGWOp_Quota_Set::execute()+0x8c9) [0x7f0e13d1ed6d]
 15: (()+0x7532d2) [0x7f0e13d4f2d2

Reported-by: Coffee Chou <coffee.zyr@gmail.com>
Signed-off-by: Dunrong Huang <riegamaths@gmail.com>