I had to bump it up to 30,000 but it finally did finish:
# ./t_printf
Content-Type: application/X-atf-tcs; version="1"
tcs-count: 6
tc-start: snprintf_dotzero
__atf_tc_separator__
__atf_tc_separator__
tc-end: snprintf_dotzero, passed
tc-start: snprintf_posarg
__atf_tc_separator__
__atf_tc_separator__
tc-end: snprintf_posarg, passed
tc-start: snprintf_posarg_width
__atf_tc_separator__
__atf_tc_separator__
tc-end: snprintf_posarg_width, passed
tc-start: snprintf_posarg_error
__atf_tc_separator__
__atf_tc_separator__
tc-end: snprintf_posarg_error, f