Make update-slave-firmware.js extremely resilient (not a single failure out of 100 updates). Add shared.js

scripts/shared.js

@@ -0,0 +1,24 @@
+require('shelljs/global');
+
+function execRetry(command) {
+    let firstRun = true;
+    let remainingRetries = 3;
+    let code;
+    do {
+        if (!firstRun) {
+            console.log(`Retrying ${command}`)
+        }
+        config.fatal = !remainingRetries;
+        code = exec(command).code;
+        config.fatal = true;
+        firstRun = false;
+    } while(code && --remainingRetries);
+}
+
+const exp = {
+    execRetry
+}
+
+Object.keys(exp).forEach(function (cmd) {
+  global[cmd] = exp[cmd];
+});