Accept files without trailing new-line
If the last line of sources file was not correctly terminated, we never
downloaded the corresponding tarball. This is different to what real
fedpkg does, which accepts the file.
When encountering unterminated line, `read` exits with non-zero code,
but it does assign the variables. Thus, if the variables are set, we try
to download the file even if read reports problem.
Based on similar commit in rhpkg-simple.
JIRA: RHELCMP-4687
Resolves: rhbz#1943593
Signed-off-by: Ondrej Nosek <onosek@redhat.com>