[FPEnv][NFC] Change test to conform to strictfp attribute rules.

In particular, the function definition is not marked strictfp despite
containing a function marked strictfp. Also, if any function call is marked
strictfp then all function calls in that function must be marked.

This change to move the one strictfp call to a new properly marked function
meets all the new rules.

Tested with a stricter version of D68233.

Reviewed by:	spatel
Approved by:	spatel
Differential Revision:	https://reviews.llvm.org/D68713

llvm-svn: 374186