ctdb-tools: Fix signed/unsigned comparisons by declaring as unsigned

ctdb-tools: Fix signed/unsigned comparisons by declaring as unsigned

These are the simple cases where a variable (usually a loop variable)
needs to be declared as an unsigned type (usually unsigned int or
size_t) instead of an int.

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