Fixup .git_ignore and configure.ac

Summary:
.git_ignore and configure.ac had some dangling references to
the qa folder. This commit addresses those.

Test Plan:

./autogen.sh && mkdir -p tmpbuild && cd tmpbuild && \
  ../configure && make -j8 && ./test/pull-tester/rpc-tests.py

Reviewers: deadalnix, #bitcoin_abc

Reviewed By: deadalnix, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D837