disk_parser: Update f2fs write_begin and write_end matchers.

Update to match upstream linux kernel.

Signed-off-by: Mohamad Ayyash <mkayyash@google.com>
disk_parse_test: Add f2fs write tests.

Signed-off-by: Mohamad Ayyash <mkayyash@google.com>
Merge pull request #661 from mkayyash/master

disk_parser: Update f2fs write_begin and write_end matchers.