MemStore.cc: silence gcc -Wunused-variable

Don't assign return value of i.get_length() to a variable until
they are really used. Added comment on what is the intention of
the variables.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
KeyValueStore.cc: silence gcc -Wunused-variable

Don't assign return value of i.get_length() to a variable until
they are really used. Added comment on what is the intention of
the variables.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>