go: sql_server_driver: Fix a race on *SqlServer.Cmd access. Start the command before we spawn its wait goroutine.

[reltuk]

No description provided.

[coffeegoddd]

@reltuk DOLT

read_tests	from_latency	to_latency	percent_change
covering_index_scan	2.3	2.3	0.0
groupby_scan	142.39	137.35	-3.54
index_join	1.93	1.93	0.0
index_join_scan	1.32	1.32	0.0
index_scan	215.44	215.44	0.0
oltp_point_select	0.25	0.25	0.0
oltp_read_only	5.0	5.0	0.0
select_random_points	0.51	0.5	-1.96
select_random_ranges	0.64	0.64	0.0
table_scan	200.47	200.47	0.0
types_table_scan	458.96	458.96	0.0

write_tests	from_latency	to_latency	percent_change
oltp_delete_insert	6.09	6.21	1.97
oltp_insert	3.13	3.13	0.0
oltp_read_write	11.24	11.24	0.0
oltp_update_index	3.3	3.3	0.0
oltp_update_non_index	2.97	3.02	1.68
oltp_write_only	6.32	6.21	-1.74
types_delete_insert	6.79	6.79	0.0

[coffeegoddd]

@reltuk DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
1ed8d4b	ok	5937471

version	total_tests
1ed8d4b	5937471

correctness_percentage
100.0

[coffeegoddd]

@reltuk DOLT

test_name	from_latency_p95	to_latency_p95	percent_change
tpcc-scale-factor-1	45.79	44.98	-1.77

test_name	from_server_name	from_server_version	from_tps	to_server_name	to_server_version	to_tps	percent_change
tpcc-scale-factor-1	dolt	b130ee8	52.75	dolt	1ed8d4b	52.81	0.11

[zachmu]

LGTM