bugfix: --backup-meta could be 0 to disable backup

[davies]

closes #2272

[codecov-commenter]

Codecov Report

Merging #2275 (147ba64) into main (f8bb61d) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##             main    #2275   +/-   ##
=======================================
  Coverage   61.89%   61.89%           
=======================================
  Files         137      137           
  Lines       25251    25251           
=======================================
  Hits        15630    15630           
+ Misses       7810     7809    -1     
- Partials     1811     1812    +1     

Impacted Files	Coverage Δ
cmd/mount.go	61.73% <0.00%> (ø)
pkg/meta/tkv.go	76.00% <0.00%> (-0.11%)	⬇️
pkg/meta/sql.go	65.76% <0.00%> (-0.10%)	⬇️
pkg/chunk/disk_cache.go	81.63% <0.00%> (ø)
pkg/meta/redis.go	71.55% <0.00%> (+0.04%)	⬆️
pkg/vfs/writer.go	79.66% <0.00%> (+1.01%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 20f2b03...147ba64. Read the comment docs.