tests: use files that actually exist

Commit af79958f1a removed
a lot of files including /home/user/test7.txt used in some tests.

Replace /home/user/test7.txt with /README.

programs/tests/t_msgget.c

@@ -55,7 +55,7 @@ int main(int argc, char *argv[])
 
     // ========================================================================
     // Generating a key using ftok
-    key = ftok("/home/user/test7.txt", 5);
+    key = ftok("/README", 5);
     if (key < 0) {
         perror("Failed to generate key using ftok");
         return 1;

programs/tests/t_semget.c

@@ -23,7 +23,7 @@ int main(int argc, char *argv[])
 
     // ========================================================================
     // Generating a key using ftok
-    key = ftok("/home/user/test7.txt", 5);
+    key = ftok("/README", 5);
     if (key < 0) {
         perror("Failed to generate key using ftok.");
         return 1;