test: fix cppcheck warnings

[alfredh]

No description provided.

[alfredh]

src/sipevent/sipevent.h:51:39: error: syntax error [syntaxError]
void sipnot_refresh(struct sipnot *not, uint32_t expires);
                                      ^
test/aulength.c:27:3: warning: Identical inner 'if' condition is always true. [identicalInnerCondition]
  TEST_ERR(err);
  ^
test/aulength.c:26:6: note: outer condition: err
 if (err)
     ^
test/aulength.c:27:3: note: identical inner condition: err
  TEST_ERR(err);
  ^
test/httpauth.c:663:9: warning: Uninitialized variable: err [uninitvar]
 return err;
        ^
test/httpauth.c:595:23: note: Assuming condition is false
 for (size_t i = 0; i < RE_ARRAY_SIZE(testv); i++) {
                      ^
test/httpauth.c:663:9: note: Uninitialized variable: err
 return err;
        ^
test/rtp.c:424:9: warning: Identical condition and return expression 'err', return value is always 0 [identicalConditionAfterEarlyExit]
 return err;
        ^
test/rtp.c:417:6: note: If condition 'err' is true, the function will return/exit
 if (err)
     ^
test/rtp.c:424:9: note: Returning identical expression 'err'
 return err;
        ^