Avoid hardcoded time limit in SHP import
Revert "Increase time limits for tests on Travis"

This reverts commit 63e71c6e152d310aff389a23e92c34756a1698d5.

The original limit is big enough, we just harcoded it in SHP importer.
Do not set memory limit in SHP import as well

- First of all current detection is wrong and it will fail on values as
  65536K.
- Also I see no reason why single import should override global settings
  we have.