IBpfMap defines all required functions of BpfMap interface.
Ex: close() from AutoCloseable
After:
AutoCloseable ---> IBpfMap ---> BpfMap
Before:
AutoCloseable -+
|
+---> BpfMap
|
IBpfMap -------+
Test: BpfMapTest
Change-Id: I5266d9bfdfcb68f632c13d214705309893dded95