Fix nasa#484, will check the lseek() return value in linux_sysmon_upd…

[myc-yang]

Checklist (Please check before submitting)

• I reviewed the Contributing Guide.
• I signed and emailed the appropriate Contributor License Agreement to GSFC-SoftwareRelease@mail.nasa.gov and copied cfs-program@lists.nasa.gov.

Describe the contribution
Fixes #484, will check the lseek() return value in linux_sysmon_update_schedstat() in fsw/modules/linux_sysmon/linux_sysmon.c

Testing performed

Expected behavior changes
When running the linux system monitor, if there is an issue going to the beginning of the /proc/schedstat file, a message will be printed out

System(s) tested on

• Hardware: PC
• OS: Ubuntu 18.04
• Versions: [e.g. cFE 6.6, OSAL 4.2, PSP 1.3 for mcp750, any related apps or tools]

Additional context
Add any other context about the contribution here.

Third party code
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Contributor Info - All information REQUIRED for consideration of pull request
Michael Yang NASA/GSFC

[jphickey]

This doesn't seem to add value. If the lseek failed for whatever reason, the later read will fail, and this will end up following the error paths from there.

While I agree that the error checking here could be better, I'm not sure this improves it. As this is linux-specific code, we should at least capture errno and print the message.

Also - as a side note - 0 is the only valid output from this call because it is SEEK_SET. Any nonzero value means it did not seek correctly.