When configure wants to show a warning, it tries to check whether the
terminal supports colour.  This check produces an error message
when running with no TERM environment variable set (seen on a tinderbox)

Fix this check so that it tolerates failure of the `tput colors` command

Change-Id: I263136142120cf66fe900df0deb74d2fa6e5d1d0
Reviewed-on: https://gerrit.libreoffice.org/57009
Tested-by: Jenkins
Reviewed-by: Michael Stahl <Michael.Stahl@cib.de>