[BUG] IPPool's allocations may not match the actual OverlappingRangeIPReservation data

[zhonglin6666]

Describe the bug
The binary whereabouts create new OverlappingRangeIPReservation, and will update IPPool's allocations.
The pod garbage collect, it will update IPPool's allocations.
If at any point, both processes simultaneously obtain IPPool,

	operation	data
the origin data	get	A B C
the binary whereabouts	update(create)	A B C D
the pod whereabouts	update(delete)	A C

the binary whereabouts update IPPool which add new OverlappingRangeIPReservation.
the pod update IPPool which delete one OverlappingRangeIPReservation.

At last, The final successful update result will overwrite the previous structure.

Expected behavior
IPPool's allocations should be match the actual OverlappingRangeIPReservation data

To Reproduce

Environment:

• Whereabouts version : v0.6.3
• Kubernetes version (use kubectl version): v1.21.5
• Network-attachment-definition: N/A
• Whereabouts configuration (on the host): N/A
• OS (e.g. from /etc/os-release): ubuntu 18.04
• Kernel (e.g. uname -a): 4.15
• Others: N/A

Additional info / context
Can the allocations in IPPool be deleted ？