[MultiDB] add mutidb warmboot support - restoring database#5773

Merged

qiluo-msft merged 7 commits intosonic-net:masterfrom

dzhangalibaba:multidbwb

Dec 10, 2020

Commits on Dec 5, 2020

[MultiDB] address review
dzhangalibaba
committed

Commits on Dec 6, 2020

[MultiDB] using cp -u option to overwrite older file only
dzhangalibaba
committed

Commits on Dec 7, 2020

[MultiDB] check if dst and src same file before cp
dzhangalibaba
committed