Eliminate false positive static analyzer warnings.

The compiler static analyzer is issuing several false positive
warnings for the file system/core/libadf/adf.cpp:
line 134: warning: Attempt to free released memory
line 240: warning: Use of memory after it is freed
line 454: warning: Use of memory after it is freed
line 553: warning: Attempt to free released memory
line 568: warning: Use of memory after it is freed
line 645: warning: Potential leak of memory pointed to by 'engs'
line 653: warning: Potential leak of memory pointed to by 'filtered_engs'

After careful analysis of the source I have come to the conclusion
that these are false warnings.  This CL annotates the source so the
static analyzer won't issue these warnings any more.

Bug: None
Test: The warnings are no longer being issued.
Change-Id: I158756b3f1eeb66f346be3cd2ffe10ebde236c80