nmeter: fix a bug with unterminated varargs
function old new delta
collect_mem 361 371 +10
collect_swp 116 120 +4
vrdval 168 170 +2
collect_thread_nr 63 65 +2
collect_int 121 123 +2
collect_if 205 207 +2
collect_fork 117 119 +2
collect_fd 79 81 +2
collect_ctx 117 119 +2
collect_cpu 621 623 +2
collect_blk 557 559 +2
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(add/remove: 0/0 grow/shrink: 11/0 up/down: 32/0) Total: 32 bytes
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>