ctdb-tests: Make integration.bash pass shellcheck

ctdb-tests: Make integration.bash pass shellcheck

Apart from the non-constant sourcing of include files.

Mostly avoidance of quoting warnings.

One subtle change is to simply pass "120" to wait_until_ready() to
stop warnings that it expects arguments but none are passed (both
SC2119 and SC2120).  There seems no way to indicate to structure
function argument handling so that shellcheck realises arguments are
optional.  In later shellcheck versions, disabling SC2120 for a
function also silences complaints about its callers... but not all of
our testing uses "later" shellcheck versions.

Signed-off-by: Martin Schwenke <martin@meltin.net>