Can't use function return value in write context in pieform renderer (Bug #1403178)

Fixing up so older versions of php (pre 5.5) can deal with it

Change-Id: I88fa8f3641d20bbf18cef7b26d43c8d14a4d6f1d
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>
Merge "Can't use function return value in write context in pieform renderer (Bug #1403178)"