Retry git clone failures

[ben-z]

Sometimes, we get the following error when cloning repos:

│ GitCommandError: Cmd('git') failed due to: exit code(128)                                                                                                                                              │
│   cmdline: git clone -v --                                                                                                                                                                             │
│ https://github.com/WATonomous/sentry-kubernetes-charts.git                                                                                                                                             │
│ /tmp/workspace/https:/github.com/WATonomous/sentry-kubernetes-charts.git                                                                                                                               │
│   stderr: 'Cloning into                                                                                                                                                                                │
│ '/tmp/workspace/https:/github.com/WATonomous/sentry-kubernetes-charts.git'...                                                                                                                          │
│ POST git-upload-pack (175 bytes)                                                                                                                                                                       │
│ POST git-upload-pack (317 bytes)                                                                                                                                                                       │
│ error: RPC failed; curl 56 GnuTLS recv error (-9): Error decoding the received                                                                                                                         │
│ TLS packet.                                                                                                                                                                                            │
│ error: 12 bytes of body are still expected                                                                                                                                                             │
│ fetch-pack: unexpected disconnect while reading sideband packet                                                                                                                                        │
│ fatal: early EOF                                                                                                                                                                                       │
│ fatal: fetch-pack: invalid index-pack output                                                                                                                                                           │
│ '      

This is usually retriable. Implement a retry mechanism.