mgr/DaemonServer: use "unsigned" to represent the pgp num

mgr/DaemonServer: use "unsigned" to represent the pgp num

as pgp num should alwayes be unsigned, and this change silences the
GCC warning like:

../src/mgr/DaemonServer.cc: In lambda function:
../src/mgr/DaemonServer.cc:2862:15: warning: comparison of integer expressions of different signedness: 'int' and 'unsigned int' [-Wsign-compare]
 2862 |      if (next != p.get_pgp_num()) {
      |          ~~~~~^~~~~~~~~~~~~~~~~~

Signed-off-by: Kefu Chai <kchai@redhat.com>