Don't share same snapshot dir for secondary access

[ryoqun]

Problem

When validator is creating a new snapshot, secondary ledger-tool use may cause the snapshot creation process to crash becuase of missing file, which is removed by the secondary:

[2020-06-03T07:15:23.428596880Z WARN  solana_ledger::snapshot_utils] tar command failed with exit code: exit code: 2
[2020-06-03T07:15:23.428623898Z WARN  solana_ledger::snapshot_utils] tar stdout: 
[2020-06-03T07:15:23.428639371Z WARN  solana_ledger::snapshot_utils] tar stderr:
    tar: snapshots: Cannot stat: No such file or directory
    tar: Exiting with failure status due to previous errors
    
[2020-06-03T07:15:24.851585353Z WARN  solana_core::snapshot_packager_service] Failed to create snapshot archive: archive generation failure exit code: 2
[2020-06-03T07:15:24.906626871Z WARN  solana_core::snapshot_packager_service] Failed to create snapshot archive: I/O error

Usually, new snapshot refers to the incorrectly shared directory via a symlink like this:

$ ls -l /tmp/.tmprqQiJo
total 1524
drwxrwxr-x 2 ryoqun ryoqun 1544192 Jun  3 16:24 accounts
lrwxrwxrwx 1 ryoqun ryoqun      66 Jun  3 16:24 snapshots -> /home/ryoqun/work/solana/testnet/snapshot/.tmpBTks9N
-rw-rw-r-- 1 ryoqun ryoqun       5 Jun  3 16:24 version

This problem is visible when doing like this:

while true; do RUST_LOG=warn ./target/release/solana-ledger-tool --ledger ./testnet/ graph /tmp/aaaa.pdf; sleep 5; done

Note that, there is still another intermittent problem which is found above one liner..

Summary of Changes

Don't share same directory snapshot.

follow up of #10209

CC: @mvines

[codecov]

Codecov Report

Merging #10384 into master will increase coverage by 0.0%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #10384   +/-   ##
=======================================
  Coverage    81.4%    81.4%           
=======================================
  Files         290      290           
  Lines       67610    67610           
=======================================
+ Hits        55081    55083    +2     
+ Misses      12529    12527    -2     

[ryoqun]

Note that, there is still another intermittent problem which is found above one liner..

For this, I'm suspecting this occurs when the validator is just catching-up, so this shouldn't be so bad....