Fix the "set -e" problem in the test-meta.sh chattr tests.

Fix the "set -e" problem in the test-meta.sh chattr tests.

Start fixing the "set -e" problem, beginning with the test-meta.sh
chattr tests, and add support to the test filesystem for options
needed by the chattr calls.

To allow us to produce a more digestable sequence of patches for the
broader "set -e" problem, temporarily establish BUP_SKIP_BROKEN_TESTS
which will do what it says when set, and until we finish repairing
everything, it must be set during any testing:

  BUP_SKIP_BROKEN_TESTS=1 make check

The fundamental issue with "set -e" is that it has some unexpected
(but documented) semantics.  For example:

  set -e
  foo() { false; rm -rf /; }

  # Effectively harmless
  foo

  # Erase the filesystem
  foo || true

If nothing else, this behavior appears to have been masking test
failures.  Better to just avoid "set -e" altogether.

Signed-off-by: Rob Browning <rlb@defaultvalue.org>