fix format string overflow in test for diag_integral write_field_aver… #611

Job	Run time
build (-DOPENMP=on, -DCMAKE_BUILD_TYPE=Release)	11m 30s
build (-DOPENMP=on, -DCMAKE_BUILD_TYPE=Debug)	3m 25s
build (-DOPENMP=on, -DUSE_DEPRECATED_IO=on, -DCMAKE_BUILD_TYPE=Release)	12m 58s
build (-DOPENMP=on, -DUSE_DEPRECATED_IO=on, -DCMAKE_BUILD_TYPE=Debug)	3m 47s
build (-DOPENMP=on, -DWITH_YAML=on, -DCMAKE_BUILD_TYPE=Release)	11m 57s
build (-DOPENMP=on, -DWITH_YAML=on, -DCMAKE_BUILD_TYPE=Debug)	3m 39s
build (-DOPENMP=on, -DWITH_YAML=on, -DUSE_DEPRECATED_IO=on, -DCMAKE_BUILD_TYPE=Release)	13m 0s
build (-DOPENMP=on, -DWITH_YAML=on, -DUSE_DEPRECATED_IO=on, -DCMAKE_BUILD_TYPE=Debug)	3m 59s
build (-DOPENMP=off, -DCMAKE_BUILD_TYPE=Release)	11m 41s
build (-DOPENMP=off, -DCMAKE_BUILD_TYPE=Debug)	3m 30s
build (-DOPENMP=off, -DUSE_DEPRECATED_IO=on, -DCMAKE_BUILD_TYPE=Release)	12m 33s
build (-DOPENMP=off, -DUSE_DEPRECATED_IO=on, -DCMAKE_BUILD_TYPE=Debug)	3m 52s
build (-DOPENMP=off, -DWITH_YAML=on, -DCMAKE_BUILD_TYPE=Release)	12m 4s
build (-DOPENMP=off, -DWITH_YAML=on, -DCMAKE_BUILD_TYPE=Debug)	3m 40s
build (-DOPENMP=off, -DWITH_YAML=on, -DUSE_DEPRECATED_IO=on, -DCMAKE_BUILD_TYPE=Release)	12m 57s
build (-DOPENMP=off, -DWITH_YAML=on, -DUSE_DEPRECATED_IO=on, -DCMAKE_BUILD_TYPE=Debug)	3m 56s
	2h 8m 28s

Provide feedback