Handle failed to fill whole buffer in blob corruption detection logic

[ikopylov]

Starting happened after changing read methods to read_exact:

2023-01-15 20:42:25  bob_common::configs::node:428 ERROR    can't initialize holder, attempt 3/3, error backend storage error: pearl error: failed to init from existing blobs

Caused by:
    0: failed to read blobs
    1: Failed to read existing blob: /opt/disk1/bob_perf/bob/0/1673776800_9JVKD4lftV/bob_9JVKD4lftV.424.blob
    2: failed to read blob header. Blob file: "/opt/disk1/bob_perf/bob/0/1673776800_9JVKD4lftV/bob_9JVKD4lftV.424.blob"
    3: failed to read from file: bob_9JVKD4lftV.424.blob
    4: failed to fill whole buffer

Specific BLOB file had 0 size