Fix TestNewModuleRegistry flaky test

[adriansr]

What does this PR do?

Fixes flaky unit test TestNewModuleRegistry.

Filesets must be sorted before comparing them, as they are originally populated by iterating on a map, which returns the keys in random order.

Why is it important?

So tests pass.

Logs

    modules_test.go:104: 
        	Error Trace:	modules_test.go:104
        	Error:      	Not equal: 
        	            	expected: []string{"error", "access"}
        	            	actual  : []string{"access", "error"}
        	            	
        	            	Diff:
        	            	--- Expected
        	            	+++ Actual
        	            	@@ -1,4 +1,4 @@
        	            	 ([]string) (len=2) {
        	            	- (string) (len=5) "error",
        	            	- (string) (len=6) "access"
        	            	+ (string) (len=6) "access",
        	            	+ (string) (len=5) "error"
        	            	 }
        	Test:       	TestNewModuleRegistry
--- FAIL: TestNewModuleRegistry (0.02s)

[mergify]

This pull request does not have a backport label. Could you fix it @adriansr? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-v./d./d./d is the label to automatically backport to the 7./d branch. /d is the digit

NOTE: backport-skip has been added to this pull request.

[elasticmachine]

Pinging @elastic/elastic-agent-data-plane (Team:Elastic-Agent-Data-Plane)

[cmacknz]

Thanks!

[elasticmachine]

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Build stats

• Start Time: 2022-02-17T15:56:56.533+0000

• Duration: 103 min 45 sec

Test stats 🧪

Test	Results
Failed	0
Passed	9478
Skipped	1107
Total	10585

💚 Flaky test report

Tests succeeded.

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