Backups, Azure, Issue 7570: Check existance of container before creation attempt

[harikb]

The code adds a workaround for a Segfault appearing deep inside the azure sdk. The code checks for the existence of a
container before attempting creation. This is related to issue #7570

Please note this code is enabled only when -DBUILD_AZURE_BACKUP=ON is turned on via cmake.

Release branches vs Master/main

Master has the affected file inside a subdirectory azure_backup. Release 7.1 branch (the release I am using) has the same file in the parent directory. I will be making a separate pull request for Release 7.1 and Release 7.2 branch.

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• The PR has a description, explaining both the problem and the solution.
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• This change/bugfix is a cherry-pick from the next younger branch (younger release-branch or main if this is the youngest branch)
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[fdb-windows-ci]

Doxense CI Report for Windows 10

• Commit ID: 3aec508
• Result: ✔️ SUCCEEDED
• Build Logs (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr on Linux CentOS 7

• Commit ID: 3aec508
• Duration 1:03:35
• Result: ✅ SUCCEEDED
• Error: N/A
• Build Logs (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr-cluster-tests on Linux CentOS 7

• Commit ID: 3aec508
• Duration 3:58:11
• Result: ❌ FAILED
• Error: Error while executing command: make -C tests -kj run. Reason: exit status 2
• Build Logs (available for 30 days)