common: fix kmemleak to work with sections

Refactor the kmemleak code to work correctly with sections.  This
requires changing the location of the "is kmemleak enabled?" flag to
use /tmp instead of RESULT_BASE, scanning for leaks after every
test, and clarifying which functions get used when.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>

check

@@ -496,7 +496,7 @@ _expunge_test()
 	return 0
 }
 
-_init_kmemleak
+_detect_kmemleak
 _prepare_test_list
 
 if $OPTIONS_HAVE_SECTIONS; then
@@ -771,9 +771,12 @@ for section in $HOST_OPTIONS_SECTIONS; do
 			# and log messages that shouldn't be there.
 			_check_filesystems
 			_check_dmesg || err=true
-			_check_kmemleak || err=true
 		fi
 
+		# Scan for memory leaks after every test so that associating
+		# a leak to a particular test will be as accurate as possible.
+		_check_kmemleak || err=true
+
 		# test ends after all checks are done.
 		$timestamp && _timestamp
 		stop=`_wallclock`