Fix static analyzer warnings.

frameworks/base/libs/androidfw/ResourceTypes.cpp:742:46: warning: Result
of 'calloc' is converted to a pointer of type 'char16_t *', which is
incompatible with sizeof operand type 'char16_t **'
    mCache = (char16_t**)calloc(mHeader->stringCount,
        sizeof(char16_t**));

frameworks/base/libs/androidfw/ResourceTypes.cpp:4359:28: warning:
Potential leak of memory pointed to by 'set'
     return NO_MEMORY;

Bug: None
Test: Builds without the aforementioned warnings.
Change-Id: I1f84c1b9f4cba05f5cc7c3ae9fec1a07bc9cd8fe