libcutils: bug str_parms.c:str_parms_get_float().

str_parms_get_float did not return the output into
*val. Only output if returning with no error. Audit
shows no internal users of this library function

(cherry picked from commit 8e71ddea)

Change-Id: I14a3f08a098072a159dd93f85ead36b3f445816f