test(perf/vsock): copy iperf binary only once

Problem: Currently we copy the iperf3-vsock binary into the guest in
spawn_iperf3_client that is called by every client (we have 2).  If by
the time the second binary is being copied that first one is already
executing, we get the "Text file busy" error.

Solution: Move the copy into the test construction to copy the binary
only once.

Signed-off-by: Nikita Kalyazin <[email protected]>

Author: kalyazin

tests/integration_tests/performance/test_vsock.py

@@ -41,6 +41,11 @@ def __init__(self, microvm, mode, payload_length):
             iperf="/usr/local/bin/iperf3-vsock",
             payload_length=payload_length,
         )
+        # The rootfs does not have iperf3-vsock
+        iperf3_guest = "/tmp/iperf3-vsock"
+
+        self._microvm.ssh.scp_put(self._iperf, iperf3_guest)
+        self._guest_iperf = iperf3_guest
 
     def host_command(self, port_offset):
         return (
@@ -58,11 +63,6 @@ def spawn_iperf3_client(self, client_idx, client_mode_flag):
                 make_host_port_path(VSOCK_UDS_PATH, self._base_port + client_idx),
             )
         )
-        # The rootfs does not have iperf3-vsock
-        iperf3_guest = "/tmp/iperf3-vsock"
-
-        self._microvm.ssh.scp_put(self._iperf, iperf3_guest)
-        self._guest_iperf = iperf3_guest
         return super().spawn_iperf3_client(client_idx, client_mode_flag)
 
     def guest_command(self, port_offset):