Add retry options to fetch commands, lets see if that helps

elabinelab setup issues.

install/libinstall.pm.in

 #!/usr/bin/perl -w
 #
-# Copyright (c) 2003-2018 University of Utah and the Flux Group.
+# Copyright (c) 2003-2019 University of Utah and the Flux Group.
 # 
 # {{{EMULAB-LICENSE
 # 
@@ -789,7 +789,8 @@ sub FetchFile($$) {
 	PhaseWouldHave("fetch $URL");
 	return 1;
     }
-    if (ExecQuiet("$FETCH -o $localname $URL")) {
+    if (ExecQuiet("$FETCH --retry --timeout=30 --retry-delay=15 ".
+		  "  -o $localname $URL")) {
 	return 0;
     } else {
 	return 1;