Set e2freefrag and e2fsdroid as required by libfs_mgr_defaults

libfs_mgr_defaults uses the e2fsdroid binary, make this dependency
explicit.
Add also e2freefrag as a dependency in preparation for filesystem
fragmentation monitoring.

Bug: 146078546
Test: m + e2freefrag on device
Change-Id: I878d1b090809861c803f6b17fbb3813e03842a50
Signed-off-by: Alessio Balsini <balsini@google.com>