Do not exit 1 from devtest_variables.sh

return 1 instead of exiting 1 in devtest_variables.sh.  This avoids
being logged out of current shell on error when sourcing the file
as documented.

Change-Id: I9b1dc5cd4ab033e96605ea5d5c7577f5cb7c8b52
Merge "Do not exit 1 from devtest_variables.sh"