scpi-dmm: use INIT instead of MEAS for Agilent to start acquisition

Though measurement values come in, the 34405A and 34465A meters kept
beeping when acquisition is started. Stopped beeping when the MEAS
keyword was changed to INIT, which is used for other Agilent devices
using the HP protocol variant.

This change is acceptable because it was tested on all DMMs which use
the Agilent protocol (according to scpi-dmm profiles).

src/hardware/scpi-dmm/api.c

@@ -43,7 +43,7 @@ static const struct scpi_command cmdset_agilent[] = {
 	{ DMM_CMD_SETUP_REMOTE, "\n", },
 	{ DMM_CMD_SETUP_FUNC, "CONF:%s", },
 	{ DMM_CMD_QUERY_FUNC, "CONF?", },
-	{ DMM_CMD_START_ACQ, "MEAS", },
+	{ DMM_CMD_START_ACQ, "INIT", },
 	{ DMM_CMD_STOP_ACQ, "ABORT", },
 	{ DMM_CMD_QUERY_VALUE, "READ?", },
 	{ DMM_CMD_QUERY_PREC, "CONF?", },