[tools][manifest_compiler] Fix argument validation

Passing the -i argument without the -o argument does not produce
the expected error message because the parser is the object that
should receive the error method call.

Bug: None
Test:
./tools/manifest_compiler.py -o a_file_name
./tools/manifest_compiler.py -i a_file_name

Change-Id: I69f34387c01aaad9edf251b81ed9e19305432494