recovery: free recovery info before stopping recovery

Without this patch, the recovery thread cannot start the next recovery
and the stopped recovery cannot start any more.

Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>
sheepdog stable release v0.7.2

Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>
fix error-io in sheepfs when using ext4 filesystem

When using ext4 filesystem on sheepfs volumes, it will print kern message:

	[171972.794292] io-error-guard: catch 1 continuous bio error.
	[171977.699795] io-error-guard: catch 2 continuous bio errors.
	[171977.707797] Aborting journal on device loop0-8.
	[171978.162038] EXT4-fs error (device loop0): ext4_journal_start_sb: Detected aborted journal
	[171978.170034] EXT4-fs (loop0): Remounting filesystem read-only

The reason is sheepfs process FLUSH opcode incorrectly. If the sheep daemon dose not
support FLUSH, sheepfs should explicitly set sheepfs_object_cache to 'false' and return
success, not return error.

Signed-off-by: Robin Dong <sanbai@taobao.com>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>
tests/functional: let check clean directories of passed tests in default

Some tests consume lots of disk space and cause disk full (at least on
my box with 64GB SSD). This patch lets the check script clean
directories of passed tests in default. In addition, this patch adds a
new option -keep-passed. When this option is passed, the script keeps
directories of passed tests. This would be useful when we need to
check correctness of test scriptes themselves.

Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>
Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>