dim: Fix substring match

When checking if a url matches one of the urls from the drm_tip_repos
array, commit faa12d34 ("dim_setup: Use "repo" for remote default
name") used a substring match. However, it's possible that a url is a
substring of another, leading to the wrong repo being returned.

Depending on the order of iteration in the drm_tip_repo array,
ssh://git.freedesktop.org/git/drm/drm would match as a substring
of ssh://git.freedesktop.org/git/drm/drm-intel, thus returning drm-intel
rather than drm as repo.

It doesn't always fail because Bash doesn't guarantee the order of
associative arrays. Running with Bash 5.2.15 it works, because it
compares drm's url before drm-intel's. However it was reported that
with 5.0.17 it doesn't follow the same order, and thus causing this
issue.

On a dim setup execution, it errors out like this:

	dim: No git remote for any of the URLs ssh://git.freedesktop.org/git/drm/drm git://anongit.freedesktop.org/drm/drm https://anongit.freedesktop.org/git/drm/drm https://anongit.freedesktop.org/git/drm/drm.git

 found in /path/to/src
	Enter a name to auto-add this remote, leave blank to abort: drm-intel
	error: remote drm-intel already exists.

Also, dim should probably start using `set -e`, because the error above
is ignored and in the end it shows:

	dim setup successfully completed!

Leaving a half-baked setup.

Reported-by: John Harrison <john.c.harrison@intel.com>
Fixes: faa12d34 ("dim_setup: Use "repo" for remote default name")
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>