test/e2e: Fix 'resource name may not be empty' failure in catalog templating test case (#2457)

* test/e2e: Fix 'resource name may not be empty' failure in catalog templating test case

Update the 'adding catalog template adjusts image used' test case and
fix the issue where get requests for the test catalogsource were failing
due to the source.GetName() and source.GetNamespace() being empty, and
therefore the test catalogsource could never be updated.

Updating the test logic to avoid overwriting the `source` variable
during every poll by suppressing the variable returned appeared to be
the culprit. This was consistently reproducible on a cluster when
focusing on this single test and running the e2e suite directly.
After making these changes, I wasn't able to reproduce locally anymore.

Signed-off-by: timflannagan <[email protected]>

* test/e2e: Replace context.TODO references with context.Background in the catalog e2e package

Signed-off-by: timflannagan <[email protected]>

Author: timflannagan