intg: Generate tmp dir with lowercase
    
    This is a workaround for buggy python-requests 2.12.4.
    It cannot handle uppercase letters in file path.
    
    The manual page MKTEMP(1) says that the parameter --dry-run is unsafe.
    It is not critical for our use-case in CI but we should revert the patch
    after fixed version of puython-request will be released
    
    Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>
    (cherry picked from commit 929bb1170931d7aafac4dc0572ce18747c919a56)