Initialize RSA context in RSA test suite before first potentially failing operation

The function `rsa_gen_key` from `test_suite_rsa.function` initialized a stack allocated RSA context only after
seeding the CTR DRBG. If the latter operation failed, the cleanup code tried to free the uninitialized RSA context,
potentially resulting in a segmentation fault. Fixes one aspect of #1023.
diff --git a/tests/suites/test_suite_rsa.function b/tests/suites/test_suite_rsa.function
index d4f3308..7cfc09f 100644
--- a/tests/suites/test_suite_rsa.function
+++ b/tests/suites/test_suite_rsa.function
@@ -667,12 +667,12 @@
     const char *pers = "test_suite_rsa";
 
     entropy_init( &entropy );
+    rsa_init( &ctx, 0, 0 );
+
     TEST_ASSERT( ctr_drbg_init( &ctr_drbg, entropy_func, &entropy,
                                 (const unsigned char *) pers,
                                 strlen( pers ) ) == 0 );
 
-    rsa_init( &ctx, 0, 0 );
-
     TEST_ASSERT( rsa_gen_key( &ctx, ctr_drbg_random, &ctr_drbg, nrbits,
                  exponent ) == result );
     if( result == 0 )