[docker] Fix libra_init to reuse cache
[docker] Fix libra_init to reuse cache

Use the same build command so the layer cache can be reused.

Closes: #2180
Approved by: davidiw

aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,libra/libra,libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core