ctdb-tests: Shell cleanups in wait_until() function

ctdb-tests: Shell cleanups in wait_until() function

This file is included by local_daemons.sh, which is not a bash script
and wait_until() uses the "local" keyword.  Prefixing variable names
with '_' to indicate that they are local changes a lot of lines in
this function.  So, fix indentation, potential quoting problems and
other ShellCheck hits while touching this function.

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@samba.org>