sheepfs/http: fix variable uninitialized in curl_get_object_size

If curl_easy_init is failure, the variable content_length will be
uninitialized. This will come into unexpected problem.

Signed-off-by: Ruoyu <liangry@ucweb.com>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>
dog: fix compile warning

It will report warning:

node.c: In function ‘node_stat’:
node.c:278: warning: ‘last.r.peer_total_rx’ may be used uninitialized in this function
node.c:278: warning: ‘last.r.peer_total_tx’ may be used uninitialized in this function
node.c:278: warning: ‘last.r.peer_total_nr’ may be used uninitialized in this function
node.c:278: warning: ‘last.r.gway_total_rx’ may be used uninitialized in this function
node.c:278: warning: ‘last.r.gway_total_tx’ may be used uninitialized in this function
node.c:278: warning: ‘last.r.gway_total_nr’ may be used uninitialized in this function

when compiling sheepdog. The reason is we forget to initialize argument 'last'.

Signed-off-by: Robin Dong <sanbai@taobao.com>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>