make-test: use api custom-dump to reduce log size.

make-test: use api custom-dump to reduce log size.

- Reduce log size by using "api trace custom-dump" instead
  of "api trace dump".
- Fix custom-dump output of cli_inband_t api message to include
  cli command being executed.

New output:
DBGvpp# api trace custom-dump /tmp/test
vl_api_memclnt_delete_t:
index: 2
handle: 0x301d8e10
SCRIPT: memclnt_create name vpp_api_test
SCRIPT: sw_interface_dump all
SCRIPT: control_ping
SCRIPT: exec show run

Old output:
DBGvpp# api trace dump /tmp/test
---------- trace 0 -----------
vl_api_memclnt_delete_t:
index: 33554432
handle: 0x108e1d3000000000
---------- trace 1 -----------
vl_api_memclnt_create_t:
name: vpp_api_test
input_queue: 0x808e1d3000000000
context: 0
ctx_quota: 0
---------- trace 2 -----------
vl_api_sw_interface_dump_t:
_vl_msg_id: 61
client_index: 33554432
context: 0
name_filter_valid: 0
---------- trace 3 -----------
vl_api_control_ping_t:
_vl_msg_id: 712
client_index: 33554432
context: 0
---------- trace 4 -----------
vl_api_cli_inband_t:
_vl_msg_id: 715
client_index: 33554432
context: 0
length: 9

Change-Id: If740c861649a3a59b8cc7a777c23c3cf94b8ff87
Signed-off-by: Dave Wallace <dwallacelf@gmail.com>