fix build failures in unit tests on some systems

• CentOS 7:

23:04:15  /usr/include/c++/4.8.2/bits/stl_algo.h:2263:35: error: no match for call to ‘(isc::dhcp::test::GenericLeaseMgrTest::testLease6LeaseTypeCheck()::__lambda3) 
(boost::shared_ptr<isc::dhcp::Lease6>&, const boost::shared_ptr<isc::dhcp::Lease6>&)’
23:04:15      while (__comp(*__first, __pivot))
23:04:15                                     ^
23:04:15  generic_lease_mgr_unittest.cc:1621:25: note: candidates are:
23:04:15           auto compare = [](Lease6Ptr& left, Lease6Ptr& right) {
23:04:15                           ^
23:04:15  In file included from /usr/include/c++/4.8.2/algorithm:62:0,
23:04:15                   from /usr/include/boost/smart_ptr/shared_ptr.hpp:42,
23:04:15                   from /usr/include/boost/shared_ptr.hpp:17,
23:04:15                   from ../../../../src/lib/asiolink/io_service.h:11,
23:04:15                   from ../../../../src/lib/database/database_connection.h:10,
23:04:15                   from generic_lease_mgr_unittest.cc:10:
23:04:15  /usr/include/c++/4.8.2/bits/stl_algo.h:2263:35: note: bool (*)(isc::dhcp::Lease6Ptr&, isc::dhcp::Lease6Ptr&) {aka bool (*)(boost::shared_ptr<isc::dhcp::Lease6>&, boost::shared_ptr<isc::dhcp::Lease6>&)} <conversion>
23:04:15      while (__comp(*__first, __pivot))
23:04:15                                     ^
23:04:15  /usr/include/c++/4.8.2/bits/stl_algo.h:2263:35: note:   candidate expects 3 arguments, 3 provided
23:04:15  generic_lease_mgr_unittest.cc:1621:60: note: isc::dhcp::test::GenericLeaseMgrTest::testLease6LeaseTypeCheck()::__lambda3
23:04:15           auto compare = [](Lease6Ptr& left, Lease6Ptr& right) {
23:04:15                                                              ^
23:04:15  generic_lease_mgr_unittest.cc:1621:60: note:   no known conversion for argument 2 from ‘const boost::shared_ptr<isc::dhcp::Lease6>’ to ‘isc::dhcp::Lease6Ptr& {aka boost::shared_ptr<isc::dhcp::Lease6>&}’
23:04:15  In file included from /usr/include/c++/4.8.2/algorithm:62:0,
23:04:15                   from /usr/include/boost/smart_ptr/shared_ptr.hpp:42,
23:04:15                   from /usr/include/boost/shared_ptr.hpp:17,
23:04:15                   from ../../../../src/lib/asiolink/io_service.h:11,
23:04:15                   from ../../../../src/lib/database/database_connection.h:10,
23:04:15                   from generic_lease_mgr_unittest.cc:10:

• Fedora 38:

rdata_unittest.cc: In static member function ‘static std::string {anonymous}::Rdata_Unknown_Test::getLongestRdataTxt()’:
rdata_unittest.cc:257:16: error: ‘setw’ was not declared in this scope
  257 |         oss << setw(2) << (i & 0xff);
      |                ^~~~
rdata_unittest.cc:29:1: note: ‘std::setw’ is defined in header ‘<iomanip>’; did you forget to ‘#include <iomanip>’?
   28 | #include <boost/lexical_cast.hpp>
  +++ |+#include <iomanip>
   29 | 
make[7]: *** [Makefile:1159: run_unittests-rdata_unittest.o] Error 1