MD5 Verification fails on HTTPUpdate after unsuccessful OTAUpdate

[CriPstian]

Hardware:

Board: esp32doit-devkit-v1
Core Installation version: 1.0.4
IDE name: CLion
Flash Frequency: 40Mhz
PSRAM enabled: no
Upload Speed: 115200
Computer OS: Ubuntu

Description:

MD5 Verification fails on HTTP Update (with no x-MD5 header response) after unsuccessful OTA Update because the _target_md5 string in Updater class is not restored to default value.

Sketch:

No need for a sketch, This is a reproducible issue by following two basic steps:

1. Fail an OTAUpdate by cancelling the update in the middle of the process
2. Trigger an HTTPUpdate with a server that has no x-MD5 header set on the response.
   => The update will fail with MD5 Check fail

Debug Messages:

MD5 Failed: expected:<_target_md5>, calculated:<md5>

[CriPstian]

I've created a small PR #4260 for cleaning up the MD5 related fields since every use of the Updater class would leave garbage values at the site

[CriPstian]

This issue continues to create issues on my side. Is anybody up for review?

[stale]

[STALE_SET] This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 14 days if no further activity occurs. Thank you for your contributions.

[CriPstian]

This issue was fixed by #4260