fix(file-system-monitor): De-duplicate `FileOpen` alerts for containers

[vadorovsky]

When reading files inside container, the file_open LSM hook gets triggered twice. Before this change, it resulted in threat alerts being issued twice in case the opened file matched a rule.

The only difference which can be spotted between struct file instances in both calls of file_open is an additional bit in file->f_flags during the second call.

When calling cat /etc/shadow inside container, the f_flags are respectively:

• 131072 (0x1000000000000000000)
• 393216 (0x1100000000000000000)

[banditopazzo]

closed as it seems the normal behaviour