tests: remove redundant settings of `errexit' shell flag

tests: remove redundant settings of `errexit' shell flag

* tests/autodist-acconfig.test: Do not set the `errexit'
shell flag, as it is already set by `tests/defs'.
* tests/autodist-acconfig-no-subdir.test: Likewise.
* tests/autodist-aclocal-m4.test: Likewise.
* tests/autodist-config-headers.test: Likewise.
* tests/autodist-configure-no-subdir.test: Likewise.
* tests/autodist-stamp-vti.test: Likewise.
* tests/autodist-subdir.test: Likewise.
* tests/autodist.test: Likewise.
* tests/check-exported-srcdir.test: Likewise.
* tests/check-tests-in-builddir.test: Likewise.
* tests/check-tests_environment.test: Likewise.
* tests/help-python.test: Likewise.
* tests/java-check.test: Likewise.
* tests/java-extra.test: Likewise.
* tests/java-noinst.test: Likewise.
* tests/lex-subobj-nodep.test: Likewise.
* tests/ltinit.test: Likewise.
* tests/m4-inclusion.test: Likewise.
* tests/maintclean-vpath.test: Likewise.
* tests/parallel-tests-subdir.test: Likewise.
* tests/pr8365-remake-timing.test: Likewise.
* tests/python-dist.test: Likewise.
* tests/python-vars.test: Likewise.
* tests/python-virtualenv.test: Likewise.
* tests/python5b.test: Likewise.
* tests/specflg-dummy.test: Likewise.
* tests/yacc-dist-nobuild-subdir.test: Likewise.