ctdb-daemon: Avoid signed/unsigned comparison by declaring as unsigned

ctdb-daemon: Avoid signed/unsigned comparison by declaring as unsigned

Compiling with -Wsign-compare complains:

ctdb/server/ctdb_call.c:831:12: warning: comparison of integer expressions of different signedness: ‘int’ and ‘uint32_t’ {aka ‘unsigned int’} [-Wsign-compare]
  831 |  if (count <= ctdb_db->statistics.hot_keys[0].count) {
      |            ^~

and

ctdb/server/ctdb_call.c:844:13: warning: comparison of integer expressions of different signedness: ‘int’ and ‘uint32_t’ {aka ‘unsigned int’} [-Wsign-compare]
  844 |   if (count <= ctdb_db->statistics.hot_keys[i].count) {
      |             ^~

Found by cs-build.

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