Fix cmdline datasource overflow

[ken3]

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Pull request description

Shell command with very long args (cmdLineSizeRet > 2048bytes) sometimes gets SIGSEGV. Valgrind reports memory corruption in snoopy_datasource_cmdline() and I have just fixed it.

[bostjan]

OMG such an obvious one, thanks @ken3!

[bostjan]

The fix is available in the 2.4.14 release.