persistence-in-db: Fix signature issue

**Detailed Description**
Persisting a transaction to the database works, however pulling that transaction back fails due to duplicate signatures.

**Actual Behavior**
Retrieving a transaction from the database results in a duplicate signature error from the java sdk.

**Expected Behavior**
It should be possible to pull a transaction back.

**Environment:**
- Java: [e.g. OpenJDK 11.0.4]
- Node: [e.g. v12.9.1-x86]
- OS: [e.g. Ubuntu 18.04]
- Version: [e.g. 1.0.1]

**Additional Context**
Add any other context about the problem here. Attach any logs here, if applicable.