bch2_count_inode_sectors() uses for_each_btree_key() internally, which
handles lock restarts - the lockrestart_do() in check_i_sectors() is
redundant, and buggy here since the count that
bch2_count_inode_sectors() returns was interpreted as an error by
lockrestart_do().
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>