Fix network initialization for HTCondor example

[vipau]

These scripts were sometimes breaking on GCE because the hardcoded sleep was not enough to set up the network before downloading packages. Both Debian and CentOS seem to be working consistently after this change.

example log line from CentOS instance Stackdriver: "Nov 25 15:18:05 condor-submit startup-script: INFO startup-script: One of the configured repositories failed (Unknown),"

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