tests: Sprinkle missing igt_exit() where needed.

Yay for breaking piles of tests.

This regression has been introduced with

commit 5782eca1e19e85a04ad402fa4094aa1b5f9c53ce
Author: Tim Gore <tim.gore@intel.com>
Date:   Wed Oct 1 13:25:20 2014 +0100

    lib/igt_core.c: disable lowmemorykiller during tests

Cc: Tim Gore <tim.gore@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

tests/gem_ctx_basic.c

@@ -166,5 +166,5 @@ int main(int argc, char *argv[])
 	free(threads);
 	close(fd);
 
-	return 0;
+	igt_exit();
 }

tests/gem_exec_blt.c

@@ -270,5 +270,5 @@ int main(int argc, char **argv)
 	} else
 		run(OBJECT_SIZE);
 
-	return 0;
+	igt_exit();
 }

tests/gem_gtt_speed.c

@@ -329,5 +329,5 @@ int main(int argc, char **argv)
 	gem_close(fd, handle);
 	close(fd);
 
-	return 0;
+	igt_exit();
 }

tests/gem_hang.c

@@ -93,5 +93,5 @@ int main(int argc, char **argv)
 
 	close(fd);
 
-	return 0;
+	igt_exit();
 }

tests/gem_ppgtt.c

@@ -230,6 +230,4 @@ int main(int argc, char **argv)
 	}
 
 	igt_exit();
-
-	return 0;
 }

tests/gem_render_copy.c

@@ -186,5 +186,5 @@ int main(int argc, char **argv)
 		scratch_buf_check(&data, &dst, WIDTH - 10, HEIGHT - 10, SRC_COLOR);
 	}
 
-	return 0;
+	igt_exit();
 }

tests/gem_render_copy_redux.c

@@ -241,6 +241,4 @@ int main(int argc, char **argv)
 	}
 
 	igt_exit();
-
-	return 0;
 }

tests/gem_render_linear_blits.c

@@ -200,5 +200,5 @@ int main(int argc, char **argv)
 	for (i = 0; i < count; i++)
 		check_bo(fd, bo[i]->handle, start_val[i]);
 
-	return 0;
+	igt_exit();
 }

tests/gem_render_tiled_blits.c

@@ -211,5 +211,5 @@ int main(int argc, char **argv)
 	for (i = 0; i < count; i++)
 		check_bo(batch, &buf[i], start_val[i]);
 
-	return 0;
+	igt_exit();
 }

tests/gem_seqno_wrap.c

@@ -527,10 +527,7 @@ int main(int argc, char **argv)
 			  options.dontwrap ? "tests" : "wraps", wcount);
 	}
 
-	if (options.rounds == wcount) {
-		igt_debug("done %d wraps successfully\n", wcount);
-		return 0;
-	}
+	igt_assert(options.rounds == wcount);
 
-	return r;
+	igt_exit();
 }

tests/gem_stress.c

@@ -914,5 +914,5 @@ int main(int argc, char **argv)
 
 	igt_stop_signal_helper();
 
-	return 0;
+	igt_exit();
 }

tests/gem_userptr_blits.c

@@ -1443,6 +1443,4 @@ int main(int argc, char **argv)
 		test_access_control(fd);
 
 	igt_exit();
-
-	return 0;
 }

tests/gen3_mixed_blits.c

@@ -533,5 +533,5 @@ int main(int argc, char **argv)
 		check_bo(fd, handle[i], start_val[i]);
 	igt_info("done\n");
 
-	return 0;
+	igt_exit();
 }

tests/gen3_render_linear_blits.c

@@ -393,5 +393,5 @@ int main(int argc, char **argv)
 	for (i = 0; i < count; i++)
 		check_bo(fd, handle[i], start_val[i]);
 
-	return 0;
+	igt_exit();
 }

tests/gen3_render_mixed_blits.c

@@ -421,5 +421,5 @@ int main(int argc, char **argv)
 		check_bo(fd, handle[i], start_val[i]);
 	igt_info("done\n");
 
-	return 0;
+	igt_exit();
 }

tests/gen3_render_tiledx_blits.c

@@ -400,5 +400,5 @@ int main(int argc, char **argv)
 	for (i = 0; i < count; i++)
 		check_bo(fd, handle[i], start_val[i]);
 
-	return 0;
+	igt_exit();
 }

tests/gen3_render_tiledy_blits.c

@@ -407,5 +407,5 @@ int main(int argc, char **argv)
 		check_bo(fd, handle[i], start_val[i]);
 	igt_info("done\n");
 
-	return 0;
+	igt_exit();
 }

tests/testdisplay.c

@@ -786,5 +786,7 @@ out_mainloop:
 out_close:
 	close(drm_fd);
 
-	return ret;
+	igt_assert(ret);
+
+	igt_exit();
 }