utrace: Fix off-by-one errors

utrace: Fix off-by-one errors

This fixes two errors:

1) memcpy() copies envc elements starting from index 1, so the number
   of elements in target array should be envc + 1. But only envc was
   allocated.

2) If original environment envp is empty, i.e. it contains only a NULL
   element, the while loop misses it.

Signed-off-by: Michal Sojka <sojkam1@fel.cvut.cz>