Fix minor memory leaks

[ekacnet]

================================================================= ==157330==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 576 byte(s) in 1 object(s) allocated from: #0 0x7f7ecd050628 in malloc (/usr/lib/x86_64-linux-gnu/libasan.so.5+0x107628) #1 0x561569188e82 in if_list_get /dibbler/Port-linux/lowlevel-linux.c:222

Direct leak of 38 byte(s) in 1 object(s) allocated from: #0 0x7f7ecd05236f in operator new[](unsigned long) (/usr/lib/x86_64-linux-gnu/libasan.so.5+0x10936f) #1 0x56156914a104 in yyFlexLexer::yylex() /dibbler/ClntCfgMgr/ClntLexer.cpp:2318

Direct leak of 22 byte(s) in 3 object(s) allocated from: #0 0x7f7ecd05236f in operator new[](unsigned long) (/usr/lib/x86_64-linux-gnu/libasan.so.5+0x10936f) #1 0x56156914a203 in yyFlexLexer::yylex() /dibbler/ClntCfgMgr/ClntLexer.cpp:2341

Indirect leak of 16 byte(s) in 1 object(s) allocated from: #0 0x7f7ecd050628 in malloc (/usr/lib/x86_64-linux-gnu/libasan.so.5+0x107628) #1 0x561569188af8 in ipaddr_local_get /dibbler/Port-linux/lowlevel-linux.c:289