gfs2: Fix memory leak of object lsi on error return path

In the case where IS_ERR(lsi->si_sc_inode) is true the error exit path
to free_local does not kfree the allocated object lsi leading to a memory
leak. Fix this by kfree'ing lst before taking the error exit path.

Addresses-Coverity: ("Resource leak")
Fixes: 97fd734b

 ("gfs2: lookup local statfs inodes prior to journal recovery")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>