Patch to insure fd is valid before close

[Gary Buhrmaster <gary.buhrmaster@…>]

valgrind reported "Warning: invalid file descriptor -1 in syscall close()" from mythsystemunix.cpp. The relevant fd's are initialized to -1 and are updated to valid fds only if certain options are set in the invocation of the function. In some cases, the fd remains -1, which results in the warning message. Silence the warning by insuring that the fd is positive (as done elsewhere in the code) before issuing the close. As this is just a warning message (no actual problem exists except for the warning message) the ticket priority/severity is set to trivial/low.

github ref: ​https://github.com/garybuhrmaster/mythtv/commit/520538417c3fd0a1741bc47aaf4a54d6233c6f4e

github git-am ref: ​https://github.com/garybuhrmaster/mythtv/commit/520538417c3fd0a1741bc47aaf4a54d6233c6f4e.patch

[Gary Buhrmaster <gary.buhrmaster@…>]

In cb944639f507aec284b59a8c8c7946b680901823/mythtv:

Error: Processor CommitTicketReference failed

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