server: More concise error messages.

On the CNI request failure, multus-cni prints out cmdArgs. In all cases, except for debug printing, this is done with %s and a special printing function. However, the handleCNIRequest is an exception for some reason. That leads to unintelligible error messages in case of CNI request failures (severely abridged):

 CmdAdd (shim): CNI request failed with status 400:
 '&{ContainerID:<id> Netns:/var/run/netns/<uuid> IfName:eth0
    Args:<args> Path: StdinData:[125 121 111 117 114 32 97 100 118
    101 114 116 105 115 101 109 101 110 116 32 99 111 117 108 100
    32 98 101 32 104 101 114 101 125 ... another 650 numbers ]}
 ContainerID:"<id>" Netns:"/var/run/netns/<uuid>" IfName:"eth0"
 Args:"<args>" Path:"" ERRORED: error configuring pod ...

printCmdArgs() should be used for this case as well to avoid huge hardly readable logs.

At the same time, the content of cniCmdArgs is always appended to the error twice as seen in the example above. The first time by the HandleCNIRequest and another time by the handleCNIRequest. Same for the HandleDelegateRequest path.

Just removing the prefixing from the lower level handlers while keeping higher level ones. The ERRORED part migrated to the higher level handler functions to preserve the overall look of the error.

k8snetworkplumbingwg / multus-cni

server: More concise error messages. #1236