Re-enable in-process unwind test.

The test was skipped for PIC boot images (the check was added in
times when those were not really used). Consequently, the test
became effectively disabled since the switch to PIC boot images.

Fortunately, the new unwind library seems to be able to handle
manually loaded libraries (not by dlopen) just fine, so the
original reason for skipping PIC images doesn't hold any more.

Test: ./test.py -r -b -t 137 -v --32
Test: ./test.py -r -b -t 137 -v --64

Change-Id: Ib48ee9f677321b91e6643debc5c0e8dfab980f00