NightlyTest: Write "sentdata.txt" files and run the -submit-aux script before

NightlyTest: Write "sentdata.txt" files and run the -submit-aux script before
sending data to the server.
 - Otherwise if the server connection fails the external script never runs.

Also, create content before initiating connection to try and decrease time we
are connected to llvm.org.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72532 91177308-0d34-0410-b5e6-96231b3b80d8