twister: ignore remapped ELF file when getting ELF name

This is usually used only when doing size calculation, but now it is
being used for extracting symbols from the ELF for testing purposes and
some issues arise with multiple ELF files found.

Simplify the code a bit to make it easy to maintain a lists of things to
exclude.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>